Well I guess it was bound to happen sooner or later with only one set of keys. Misplaced and of course she's all closed up for the winter with the door handles and deadbolts locked as well as the hatc...
After trying every other key ya own, in case one might work, does it have a typical escape window? The one with the little bar that locks it or props it open. You might? be able to slim Jim into that window and pop the bar up in which case you could crawl into it.