I had an entire flat of Black Plum/Isis Candy tomatoes that was taking a LONG time to come up...couldn't figure out what the hell was going on; as all of my other tomatoes were germinating in 3 - 4 days (saran wrap/warm floor method). Turns out I had forgotten to put any seeds in the flat...
Guess that one was MY fault. :-)
Yep. Done that too, LOL!