So yesterday I made a stop to the mailbox on my way home. And what did I find in it? The key to the parcel compartment. And what was in that compartment? My travel guide, yes.

So, I don't know. Maybe whoever got the key saw the package wasn't theirs and just put the key back in the mailbox for the mailman to find. Maybe the mailman forgot to leave the key altogether. In any case, I have my book now and I am extremely pleased!