Missing Mail

We did not receive mail on Saturday August 17.The Informed delivery showed 2 very important pieces of mail that should have been delivered.The mailman did not know where Saturday's mail was.We also did not receive mail on Tuesday, but he delivered Tuesday's mail today, Wednesday.I don't know what to do. East Liberty post-office said they will look for it, but did not see it anywhere.Does anyone have my mail? 1121 Heberton StreetAny advice?Thank you Lynn Raith