Hi Mark, thanks for the extra info. If the switch was wired the same and worked to turn the original light fixture on and off...then the capped black wire at the ceiling electrical box: this configuration alone does not add up to switching power to the light fixure thru the switch. Sounds like the capped off black wire in the ceiling box should be wired to the REAL hot wire that is hopefully still somewhere up inside the ceiling box....my suspsicion is that the other hot black wire that should be twisted togther with the black wire you found capped off came loose as you were removing the old light fixture. Look carefully in the ceiling box with a good flashlight and see if you can locate it...It looks like your switch was switching the hot side of the 110 volts via the red wire and the 110 source was the black wire coming from the ceiling fixture!!! Check this out further and give me a quick reply on what you found. Hope this helps...The capped off black wire in the ceiling box by itself does not make sense...and it must have been tied to another black wire that is hot. DId you check your circuit breakers to make sure none were tripped? Post back up with more info..