This Could Only Have Two Outcomes

 I went for a jog, friday, which also happens to be trash day.

Less than 100 feet into my run, I spotted a letter in the middle of the street.  I stopped, peered at it and saw that it was addressed to my neighbor.  I shoved it into their mailbox and continued on with my run.

Later, as I was running, it occured to me that maybe the mailman didn't drop the letter in the street.  Maybe it was a piece of junk mail, it had gotten thrown in the trash and then ended up in the street when the garbage was picked up.

Which is more likely:

My neighbor will be confused about how a letter he threw away, ended back in his mailbox.

OR

My neighbor will not remember/notice.