back in the bad old days when I knew nothing about adjusting rear derailers, a similar thing happened to me. I was about 10 miles out though on the Berryman singletrack. It made for a long hiking back., mostly uphill which sucked hehe
In hindsight, I was stupid. I was having chain problems along the trail, kept jamming and stuff (chain suck I have found out since) I kept riding it like that. Boy, what a mistake.
Not saying thats what happened to you pwrd. just my experiences of what I put my own poor bike thru. hehe