CYMA AKs74u upper receiver problem

[ztara]

right, this is incredibly specific and i dowt anyone who doesn't have the exact model will be able to help really.

My problem is thus, just got my second hand CYMA AKs74u and was very happy,so opened the top (which is spring loaded) to pop in the battery and the spring loaded bolt that pops the upper receiver up (and holds the upper handgrip in) flies to the other side of the room. iv think iv got all of the parts (a steel bolt, and a small, thick spring) but they wont fit. I dunno if any thing has sheered off that could hold it in or if i'm doing anything wrong but without it the top of my handgrip comes off. Whilst this doesn't effect the gun id like to fix it!

Thanks in advance Will.