I suppose anything's possible, but I honestly don't think I started knitting the wrong way. I *know* I did that when I first began knitting, and noticed something funky going on. My knitting friend showed me what I'd done.
Since I'm doing garter stitch, the working yarn is ALWAYS in the back, and I don't think I got that mixed up. I'm thinking I did something else weird. I could have knit into the stitch below, or maybe didn't slide the stitch completely off the needle as you suggested.
If it happens again, maybe I'll attempt posting a picture, which I've never done before.
Thanks for your ideas...I'll try to be more attentive and see if I can figure out what's happening if the problem comes up again. My 6yo son is VERY intrigued by my knitting, and wants me to teach him. THAT would be interesting.