We stopped by there today on the way home in the rain. From what I could see there is a very short piece of rope hanging from the mallion. We are talking about 5 meters of rope here. Considering your situation, I don’t think you made a bad choice in cutting your rope. Assuming you had a 60 meter rope to begin with, you now have a 55 meter which will be fine top roping or leading the majority of routes in this province. Leaving behind (on the ground) 45 or 50 meters of rope would likely have been a big mistake unless you were able to go back right away with some help for retrieval. Roadside Wall is just that, beside a road and it is a common party area for the youngsters. Had you left it, one of them might have come along and got themselves into some trouble or just cut it and taken it in which case you would have had no rope at all.
I think you made the right call.
Now for the crazy part........
Stacey took a photo with her 18x zoom and here is what the rope looks like in the mallion.....
It appears as though it somehow knotted itself as you were pulling it.