It sounds as if the automatic rear hatch mechanism detected something was in the latch and prematurely locked the latch without your rear hatch being closed. Your rear hatch lock rod is now bumping up against the already locked mechanism. Try pulling down the hatch to the almost closed position and hit the remote unlock button twice....then grip your hatch's handle as if you are opening the door. This may trick the body's lock latch to open.
Second option is to lower the rear hatch, insert the key and try unlocking it manually with the key. This may also trick the body locking mechanism to reopen the locking set. Good Luck!!