I was at the library, and walked up to the lady behind the reference desk to tell her about the trouble I had in pulling up the E-book on my laptop the way she had told me to. How could I have said, I've encountered a glitch in a natural, idiomatic, or informal way? I (was) faced (with) a glitch is another way of saying the same thing, but is there a more informal way of saying it? Can I say, I hit a glitch or I was hit by a glitch?
You can hit a snag, but I'm not sure you can hit a glitch, or even face one.
You find a glitch, or more formally, encounter one.
Your first thought, "I [or I've*] found [or encountered] a glitch" would seem the simplest way to get the message across.
If you want to appear less certain as to whether it's a software bug or user error, you could say
"I think I've found a glitch".
I think "glitch" works overall because it implies no distinct blame or cause, user error or software bug. It tells them there's an issue, but it's vague enough an introduction that the next step is further triage to find exact symptom & the root cause.
*I have no preference there for informal speech, take your pick.