Why won't my subs work?

I have two 15" Rockford Fosgate P2s and an alpine MRP-M1000. I have my subs wired to 4 ohms so I don't blow them or my amp. They were working fine the other day and then I took my blazer to Wal-mart to get my tires changed and when I got my blazer back my subs wouldn't work. I checked the wires in the box thinking it might be them but they weren't loose and my remote wire isn't loose from my amp and it can't be my power wire or ground wire because my amp turns on. Anybody have any idea why they won't work?