Am I missing something!?!?

[Engels Rojas]

Good morning ladies and gentlemen,
Back in early February I put an offer in for a two family. My offer was asking price, but my closing day would've had to be a month longer than usual. Well my offer was rejected. The property closed last week for $12K less than my offer. I'm still really new to this (haven't closed my first deal yet) so, am I missing something? Is a month too much of a deterrent, what are some things that will let you (as a seller) pass on $12K?