It wasn't a pinch flat, was it?
 

I had my first flat the other day. Fortunately, I had practiced just a week earlier at home and was comfortable swapping the tube and using the CO2 out on a ride and was able to get home without problem. I'd ridden over some glass a couple blocks earlier (didn't see it until too late) and, while on the side of the road, I tried looking for the puncture, both on the tire and the tube, but couldn't find anything. I haven't had the opportunity to check the tube again, but will soon. The tire and new tube are holding pressure just fine.

Not being able to find the puncture has me wondering...Just how soon would a tire puncture and deflate if I pinched it? Would I know rather immediately or could it stay inflated for a significant amount of time? Could I have possibly pinched it when practicing and then, a week and 3 rides later, had it go flat?

Probably a dumb question, but as I said, this is my first flat, and I've only replaced the tube twice (including my practice). I'm clearly still learning.

Pump that old tub up, and run it by your lips, or under water, to find the culprit!

Just air up the punctured tube and see where the air seeps out lol

First, you can find the leak by inflating the tube (outside of the tire) and immersing it little by little in a basin of water going around the whole tube. You will see the steady stream of bubbles coming out of the hole. If the stream of leaking air is fairly strong, you can run the tube by a sensitive area of your skin (like just below your bottom lip) and feel the air escaping.

Second, pinch punctures or weak spots in a lightweight tube that just give up and open spontaneously can result in either slow or fast leaks. There is no rule. Over time you will get all kinds.

Are you lazyass wanderers ;) saying it's a possibility I could have pinched it a week ago and almost made it through three rides before it abruptly flatted?

Definitely. Tubes resist puncturing up to a point. Often the culprit (glass, stone, etc.) just "worries" the tube over a long period of time until it finally opens up.

Thanks, all of you, for your expertise.