The PCMCIA card release button will not remain inside of the laptop unless there is no card currently situated in the laptop. To get the button back in with the card in place:
1. Remove the card from the port.
2. Push the button back in to make it stay flush with the case.
3. Put the card back in the laptop.
If the button will not remain in the recess after the card has been removed, either the port release mechanism is broken, or there is something still in there. If it is broken, the PCMCIA port is very simple to replace as there are 4 screws holding it in place and then pull it from the plug connected to the motherboard to install a new one, but you will have to disassemble the laptop to get to it, and will take some time to do.