Today we actually don't know, Otto Günsche, one of Hitler's attendants did comfirm there were two pistols in the bunker room at the time of Hitler's death, one of which Hitler used to kick the bucket.

It's likely these guns were taken as sovinears by Gerhard Welzin, an adjutant to Athur Axemann (head of the Hitler Youth). Welzin was captured by the Soviet's and later died in captivity. This could mean the guns were taken by the Russian, however beyond this the trail is cold.