If it's totally stuck I usually dump it into a paint strainer bag in another pot and do an impromptu BIAB with the leftover wort.
Sometime stirring helps, but I'm guessing you've probably tried that.
If you don't have a strainer bag try using a colander to get as much liquid out as you can without too much grain.
Once they're stuck you're pretty much screwed. At that point you're just trying to salvage the wort.