I think you might be ok. If you have a LHBS close I would make a run for more yeast. If not 4-6 hours work could possibly be "spoiled" literally if the yeast gets infected. $6 to replace it.
My guess is you should be fine if you brew in the next day or two, if you wait a week or longer to use the yeast, I would throw it out and get new yeast.