When Ricky accepts the offer to take Marina out to search for painkillers for her toothache, she puts on a tiny white dress that only goes down to the tops of her thighs and only just barely conceals her crotch and buttocks in order to cover her completely naked body underneath it. When they both return to Marina's apartment, she takes off the dress, but now she is naked except for a pair of white panties that were not there before.
When Ricky first takes the knife from the store, he puts it in his back pocket. When he gets on the bus, however, there is clearly no bulge where the knife should be in his back pocket.
When Ricky goes out alone to get medication for Marina, he locks the apartment door and puts the key chain in his pocket. When he exits the front door of the building, however, it is hanging off of his belt.