I missed feeding time and my goldfish were sleeping by the time I got to them. I thought it would be better to let them be and just feed them the normal amount at feeding time the following day. Was this the right thing to do?
Yes, you did the right thing.
There's no telling if the fish would have woken up to eat but most likely not, meaning that the food just sits in the bottom and detereorates, fouling the water more.
Remember that these are fish, they will not die if you don't feed them for a day. Heck, there's stories out there of fish surviving a month with no food (they died when their owners overfed them after their starving situation).