Axle popped out of differential need help!!!

Hey guys so I noticed that my axle popped out of my differential. I jacked it up and noticed that the right side trailing arm or swing arm (not sure what it’s called) had some play in it and the other side did not. Could this of been the cause for this? Does the axle just clipped into the differential? I’m knew to this so would like to see if anyone else may have had this problem. Thanks guys!