2001 Trooper bad tranny leak, then nothing

OK, here is what happened. Was driveing the trooper one day and the trany light came on and the thing started to slip. When I got out I noticed out it had trany fluid leaking out on the pasenger side of the trany. So I towed it to the house and a couple weeks later decided to fill it up with fluid and see where it was leaking from. So i filled it up with fluid and I could not find a leak anywhere. It shifted fine at first but after it warmed up it slipped a little bit. So, I parked it and was going to change the filter and see what happens. Anyone have any ideas why it would leak the fluid out and them not leak after refilled it?

Ralph