Let me just say (in defense of the hypothetical person who did this for his hypothetical son in this hypothetical situation) that there is someting to be said for having the parts. My dad made a pinhole in each of my star wars figures weapons and attached the weapon via fishing line to the charcters hand..(via another pinhole) It pissed me off at first, when I wanted Luke to disarm the stormtrooper and steal there blastter...and while he could, he could not go more then a foot from the trooper...years later...when all my friends didn't have one weapon left for their figures, and I still had all of mine, I appreciated it....surely glueing a JM so it can't transform is going to an extreme...but lets not be to harsh....In taking after my dad I have glued parts of my sons's Zoids...I try to leave them so he can customize them..but at the same time use enough glue, and metal pins so the main beast stays intact and functioning...let me tell you..it takes about 3Xs the amount of time to "Kid proof" them as it does to build them...but my son is 7..and hasn't lost a Zoid to damage yet!
Now...as for the glue....get some model seam knives....the ultra thin saws like WMCheng shows from Hasegawa to redo 1/72 scale seam lines....then.....I would suggest a pin vise and the seam saws to slowly...carefully free it up...work from the bottom...so if you mess up its less visible.