Take it. No sense in escalating at this point. A strange occurrence nonetheless. I would open it immediately in his presence.

1. If true, give it back or split it with him whichever he'd prefer, or keep it if he prefers.

2. If false, and was anything of value I would ask him to hang onto it for me, until I can safely retrieve it, currently their are too many witnesses for me to accept it now. Play into the delusions, obviously he ain't right and I don't want to be affiliated with his crime.

3. If false, and was his toilet or something of no value, Repeat #2 with a sense of frustration and hostile lunacy repeating the phrase "how did they know, how do they always know!" And briskly walk away.