Well, what's the doorway doing there? I mean, unless you're following the Doom video game design school of architecture, there's got to be some way to get through the door, or else there's no reason for it to be there.
Logically then, there'd be some way to open it, especially if the person who put it there is alive. You could give the PCs a spot or search check to find the hidden switch. Even if the creator is unaffected, he/she/it may want to bring someone back, and it'd be easier than having to dispell the spell, just to put it back up all the time.