Without knowing your family history or anything it could have just been your Austrian last name.

It wasn't an exact science; so when the Bureaucrats went through the lists it could have been as simple as "Novák.. has to go. Müller... can stay" When actually Novak might have spoken primarily German, and Muller spoke Czech. I know it's not as simple as that, but Czech was so mixed that any census couldn't have been 100% accurate.

I doubt that schools teach that all Czechs had to leave the Sudetenland, as this is simply untrue and quickly revealed by an internet search yielding several articles or even a cursory glance at the relevant Czech wikipedia article.

As for your question, following the Munich crisis in 1938, there was no single German policy dictating in detail what would happen to the local populace bar the general aims of suppressing Czechs and the establishment of Sudetenland under German rule.

Konrad Henlein's Sudetendeutsche Partei and its sympathisers had begun a campaign of intimidation and violence against local Czechs even before Munich, and following the secession of Sudetenland to Germany, their harrassment of locals, Jews or those with anti-SdP sentiments and efforts to forcibly remove only grew bolder.

Although mostly indiscriminate, the attacks did have the aforementioned underlying aim of taking control of the region, and as such influential locals or official institutions were often targeted. These actions were later backed by official German policy, which saw the SdP become the sole political party in the annexed borderlands, and an extension of the NSDAP.

By November the most violent period was over, but the destruction of Czech public life was only beginning. People suspected of anti-German sentiments or disagreeing with Sudetenland becoming a part of Germany were forced to leave. Czechoslovak laws and remaining offices had already been abolished in the early days after Munich, and the closure of Czech businesses, schools or even cultural or entertainment venues followed soon afterwards. Even the use of Czech language in public spaces was forbidden, with German becoming the official language. As a result, tens of thousands of people kept fleeing Sudetenland to what would later become the Protectorate of Bohemia and Moravia.

The establishment of the Protectorate on March 16 1939 saw a decline in the number of Sudetenland refugees, and further development in the issue of the remaining Czechs' fate. In 1940, legislation was passed making all Czechoslovaks living in Sudetenland by March 16 previous year Protectorate citizens, while those inhabitants of Sudetenland who had claimed German nationality became citizens of the Reich.

Even then, the Germans did not have a clear answer to the question of what to do with the Czechs in Sudetenland. Suggestions ranged from granting them some minority rights – it is perhaps important to note that the Czechs in German Sudetenland were worse off by far than the Germans living in Czechoslovakia before Munich, as those enjoyed standard legal protection as well as inclusion in politics – to returning to an active and violent relocation campaign akin to the first days of the occupation, or even Germanization on a massive scale and the removal of Czechs not only from Sudetenland but from the rest of the country as well.

This third option seems to have been the endgame of Reinhard Heydrich and later Karl Hermann Frank, but the defeat of Germany prevented these plans from coming to fruition, as any definite solution to the Czech question was to be implemented only after the conflict. However, efforts to that end still continued throughout the war and affected Sudetenland as well. The effects of Germanization were felt particularly strongly there, and undesirable people kept being persecuted or forcibly relocated. Additionally, several thousand Czechoslovaks were moved in the opposite of the usual direction, that is to Sudetenland, as forced labor.

In the end, the Germans identifying with Hitler's regime or local collaborators who welcomed the changes in Sudetenland simply kept on living there, in fact they would have been better off. Conversely, many Czechs would move away from the region, or be moved. However, with limited prospects and quite possibly nowhere to go – particularly after the Protectorate was established – some simply remained in the Sudetenland and quickly turned into barely second class citizens.

If you happen to know Czech or have someone in your family who speaks it, there is a neat work covering this exact question available here: Displacement of the Czech population from the "Sudetenland" in 1938.