Hello Katie Joe....

Sometimes chit happens. Its hard to say what may have happened, but limp wristing will contribute to the slide not returning fully to battery.
I agree with the mature flatulent one. Chit happens when shooting. Not often but it happens. If you have access to YouTube there are some videos out there giving instruction on how to clear semi auto malfunctions. A little bit if knowledge in that area will give you some confidence you can deal with stuff like that.
As Imaoldfart mentioned, it could have been from limp wristing. It could happen when when a gun gets really dirty. If could happen if the round you are shooting is out of spec. It should be a rare occurrence but it will happen eventually to all of us.
Knowing how to deal with this sort of thing is part of shooting. Knowing how to deal with it safely is really important.
Once again, if you watch a video on it, it's not hard. It just not something your going to know without a little instruction.
Take care. Good luck and stay safe.