Update....
Well, they were in the filters again. Only thing, I learned something new today in my fire eel handling, lol. I put my hand into the filter and slowly under the eel. Only this time he decided to launch himself out of the filter and tank, lol. He went flying to the right, and off the side of my bed, and onto the floor, lol. Luckily it's carpet, so it was a fairly soft landing, lol. Then, when I went to pick him up and put back into the tank, found that he has razor-sharp spines down his back, lol. Ouch. That really hurt, lol. But I got him in the tank with minor problems, lol. The biggest being, he's almost as fast on carpet as in the water, lol. Kidding. But he did slither quite well across the floor, lol.
After I got them out, hopefully for the last time, I decided I would outsmart them. Lets see if it works. I plugged their hole up with filter floss, lol. Now when they try to get in there, all they will find is a wall of floss, lol. hehe.....
Edit:
Well, that didn't work, lol. They still got into the filter, lol. So today I stuffed more floss in there, and also small clumps of floss in any crack and corner. Will give it one last try. If they still get in, they are smarter than me, lol.