What happened,!! ford ranger 2002 overheated but guage read normal?

i was driving to day, about an hour and a half, and suddenly i heard a hiss sound, my truck was still running and i was close to being home so i kept driving, when i stopped on the offramp my engine was rattling, its a normal noise when it is hot out for my engine to have a rattle but this was much louder, i also noticed i had very little power and my oil guage was shaky rapidly, i limped it the last half mile and tunred it off, there was steam coming out from where the hose connects to the radiator and it seemed hot but the termostat read normal i put a big fan over it on high for a half hour then opened the radiator cap, i couldnt see anything and there was none in the overflow, it sounded like it was boiling though, i added water and let it sit, half hour later started it and it idled normally? was i out of coolant? why did it not reald as over heating? why did have loss of pull/power from the engine. its 116 degrees to day and i was driving on the freeway could this have anyting to do with it? 2002 ford ranger v6 auto 3.0