stuck!

I put some tires in my backseat to have them put on a couple weeks ago. I covered the seats with a blanket and I made it stay in place by lowering the back seats and then sticking the sheet above them and into the trunk.

Now I can't get them out one one side . It looks like the sheet is wedged into the clip that keeps the back seats in place...I've tried brute force but it's a rather think sheet and it's definitely not coming out. I also just cut the part that wouldn't come out and you can't see it unless you look in the trunk now...

Any suggestions on removing it? I've never disasembled anything back there...and yes, I know I'm retarded for getting it stuck there!

I can try to get some pics when I get home from work. Basically, I stuck a sheet over the top of the back seats in between the back plastic headrest looking piece and where the seat locks into place where the trunk is. If you look at the backseat, there are latches that you can pull that releases the lock which holds them upright. I'm pretty sure that the sheet I stuck in there is stuck in that locking mechanism that holds the back seats in place. I got it unstuck on the driver-side back seat, but it's still wedged into the passenger side back seat...

I was taking another look at it yesterday and I think I'm just going to have to tear it out (the sheet) with some extra help...unless there is another way, but I can't figure it out.