A/C fuse seems to be missing?

I went to a mechanic earlier today because I wanted to get my A/C fixed. They said my compressor wasn’t turning on at all and it would cost me about $807.00 to get it fixed so I had to say no for the time being. I went home and checked my fuse box and low and behold, spot 4 (A/C) wasn’t there.

I grabbed the spare 10 fuse but I soon realized that it kind of just sat there and you could pull it out without any effort. I checked another fuse to make sure I wasn’t going crazy and saw that there was something holding the fuse in place. Spot 4 didn’t have anything to hold the fuse in and I was wondering how in the world I’d have to buy or do to allow it to stay.