Since the German currency was so unbelievably weak at this time, was there anyone who "bought" say, a few hundred dollars worth of german marks and held onto them until economy recovered?

That would probably be a terrible idea. Your "hundred dollars worth of german marks" would be next to worthless within days. And they would never regain their value.

Furthermore, the market price of German currency would already take into account the market's expectations of future inflation or recovery. Therefore the arbitrage potential by buying-and-carrying is rather limited anyway. E.g. if today was hyper-inflation, but tomorrow everything would go magically back to normal, then somebody (aka the market) would buy German Mark in just this expectation. Therefore the market price of Mark would increase until it approaches the level of tomorrow, in anticipation of the magical recovery. It is only then that the incentive to buy mark is gone. Therefore, (at least in theory) the market price of today is already the "fair" price given the available information. And therefore, buying Mark today is ultimately pointless because there is no notion of recovery attached to it which is not already included in the price - unless you have secret information. However, such a magical recovery of the paper-Mark never really happened.

The recovery from the hyperinflation was by introducing an all new currency (Rentenmark, 1923) as the old currency was considered damaged beyond repair. The conversion rate was 1,000,000,000,000:1, so you can probably see how easy it is to lose money with currency bets when such factors are involved. Theoretically, the government could have deflated the currency back to sensible nominal amounts (nominal amount=the number you see on the bill, e.g. most people don't like to pay for a loaf of bread with 50,000,000,000 Mark for reasons of sanity). However, this would have taken generations, unless done at breakneck speed and deflation has its own perils as we know from other countries. Also, the old currency's reputation was gone for good anyway, so a fresh start had a lot of merit.

If you are living in country with high inflation, then there are ways to avoid its effects, e.g. shops can just inflate their prices at the global rate of inflation and their physical assets (the products on the shelves) are not affected at all because their value is based on physical utility. There are still costs attached (e.g. you cannot keep up with the global rate perfectly, so there will be marginal losses, and you have extra work, e.g. due to the work of repricing), but in principle you can do fine. This also holds for people who own stocks, as the companies they own stocks of will apply the mechanism described above. This does not mean that stock holders like inflation, they are just not as affected by it as people who put their trust in saving accounts. Those are just annihilated.

If you have a lot of debt then inflation is a wonderful thing, as the debt becomes less valuable by the day. E.g. if you have a million mark of debt at the start of the inflation, then at the end you can repay it with one bill of worthless cotton-paper. So a timetraveller's dominant strategy would be to take on as much debt as possible before the start of the inflation and buy stocks and property and then wait for the inflation to save him.

Obviously no sane economy can continue its operations in such an environment so even the people whose debt was essentially cancelled would still be affected by the economic recession that hit Germany, but they might make a net profit still.