there's a trick we use in our puppy classes, and it might come in useful for future situations like this
dont touch the item (toy, squirrel, whatever) and dont say anything, just hold the dog by the collar (might need slightly more strength for a big paw) dont let her lay down, so she has to just sit/stand there with it in her mouth, without being able to play with it. eventually she will drop it, then you tell her drop (or whatever command) and move it out of the way before she grabs it again.
this has worked for every puppy in my classes, except an english bull terrier, and he took 49 minutes to drop the toy.
ha ha good luck!