As mentioned in a previous post these terminals have a barb on them that is pushed in by the socket body as it enters and springs back into position when it gets to a little pocket. This holds the terminal in the correct position, sometimes this little barb can be pushed in enough to allow the terminal to come out the way it went in. You may and I say may be able to insert a small screwdriver or something similar from the other side of the terminal housing and depress this barb.
If not you will have to buy a new plug and cut the good wires and crimp them onto new terminals. Obviously a socket from a wrecker would have all the terminals locked into position and you would have to splice all your wires to the wires in the plug from the wreckers.
Amplifier part number is: 05136097AA, I will recheck it.