There's a spring mechanism that pushes it out. It worked by pressing in to lock it and then pressing in again to unlock it. The cover is recessed relative to the case, so it would be a bit difficult to secure it with tape unfortunately.

I had to end up using a small drop of superglue.

superglue is a no go there... I repair such things using tamper evident seal (those red/blue varnish for tamper proof screws etc)