If it's a actually a cultivar of P. cerasifera (Cherry Plum aka Myrobalan) and not a seedling, I'd guess that it was 'Lindsayae'. A common cultivar planted on streets because of its pretty pink blossoms. I've only seen that cultivar in Canada. Not sure of a source in the US. If you wouldn't mind seedlings, P. cerasifera is often sold as rootstock. Here is a link that might be useful:

You can cut off the damaged part and eat the fruit. The worm was a larva stage of either Plum Curculio or Oriental Fruit Moth. Look them up. You need to spray. If, they can damage all the fruit in a day or two by laying eggs on the fruit and the larvae do the rest of the damage.

Need some more info like where you are located? Sounds like cambium issues from early spring temp flux from warm day to cold night. I lost a few plum and apricot trees this year at several different sites. It's really strange how this happens when there was no real unusually rapid temp drops. I think trees that are in very wet soil going into hardening off for winter are more susceptable but the trees I lost this year don't fall into this category.

rockfarmer: I know they're not the best (or even close to it) nursery around, but at the time I paid I think $6.98 ea. for all the trees I've got from them...now their prices are as high as quality nurseries. As far as the varieties available they are exactly the same now as they were then (4-5 years ago). I would never recommend ordering from them, but contrary to reports here my experience with their customer service was very positive and I have a great plum tree from them. So all in all, I probably got what I paid for. Also, ALL the free trees I got from them (little tiny sticks) ALL grew and grew well, they were also ALL correct in their identity. I gave a free red maple they sent me to a buddy and it has since grown to a beautiful tree. To buy a red maple of that size and quality ( size it is now) from a good nursery would cost you at least $150. So, they have a place and I think generally try to do a good job.