Detective/Retardation

A brief memory lapse? That's the most obvious explanation.

But it doesn't explain why/how I gave him the first two bills separately from the rest of the stack...

He was probably just thinking about something else.

Oh, so I was on an expedition after all.

Added 3 minutes later
By the way, on the second day, I almost got robbed by "bandits." So, everything adds up. It's a shame I didn't boost my stats before the start of the game.