Some of the UPS drivers working my beat will mark packages as "delivery attempted - customer not available" (or "signature required") when they run out of time for the day and didn't really even try the delivery. Marking it this way makes their numbers look better than marking it as delivery not attempted. I've had it out with the local depot several times on this one. I know they aren't really attempting delivery because (1) there is never a notice left, (2) there is a big ole' sign on my door giving them a safe location where they can leave packages just steps away that all the drivers honor and (3) they never have a problem delivering it and leaving it in the said safe location the next day, even when I'm not home. I've even been home the entire day several times when packages have gotten marked this way...
So my guess is they will eventually deliver it in the next day or two, and no signature will be needed.