I'm putting my money on a BFP.
A few years back, I took an FRER and watched it until the test line appeared. It was *clearly* a BFN, so I pitched it into the basket. The next morning, I took the test out of the basket and there was a faint line.
I took another test later that afternoon and there was that line again!
That line is napping on the livingroom chair right now.