I am so sorry for your loss!! My first betta jumped out of a container off our cupboard when I was cleaning his tank and landed on ceramic tile floor and was there for at least three minutes before I came back and noticed. Fortunately he only had minimal damage to one of his fins and lived for two years after that!! So I have learned to always have a cover!! Also the betta of mine that passed recently had his tank knocked over by my curious cat and was laying on wet carpet for a while before anyone noticed and he also survived and lived for almost a year after that. So now my new betta is in a room where the door is always shut so my kitty can't be curious any more!
Good luck if you decide to get a new betta!!