So what's up with this last bore

it can only keep 43 cores total and there are less than 10 slots left. Maybe after the abrasion and dust analysis they decided it wasn't interesting enough.

are they abandoning any thought of retrieving it?

Long answer:

I could go on about this entire part of the mission for several posts, but suffice it to say that abandoning this sample is a matter for tears, not shrugs. Trust me on this. The backtracking required by Percy to reach this spot was incredible, possibly unprecedented in planetary exploration (the only comparable example I can recall came at the beginning of Curiosity's mission, but that was a lateral move and not a true backtrack).

The basic problem we have here is that most of these amazing "spotted white" rocks here are too small, and appear to be too rough, for similar coring attempts. Aside from this big one we've already tried, there aren't many solid-looking ones to choose from:

To be honest, I wasn't sure that abrading was going to work well in the first place, as I believed the rock would be pretty hard/tough, but I was pleasantly surprised by how clean and well-defined the abrasion patch was. Between that, and the huge and somewhat unusual number of photos and geochemical measurements they took here, I can assure you that the science team was highly interested in this material, which has never been seen by any rover before, certainly not before this mission.

I cannot emphasize enough how much of a "detour" this sample and the entire visit to this area has been. It was never part of the original plan for exploring this area (we're a fair bit northeast of the "Lac de Charmes" marker at the moment), which involved getting two samples down at Lac de Charmes - and those were supposed to be bedrock samples, not "float" rocks (clasts) like this one. To date, they didn't take a single one! And now, here they are, on this huge detour. I would gladly give up one of our six remaining empty tubes to get a sample here, no regrets, no matter what we find later. Exciting times!

They drove off today, did I miss it or are they abandoning any thought of retrieving it?

Short answer: yes, it appears they have given up on this particular sample. The rock simply didn't cooperate - its hardness is apparently such that it allowed the drill to penetrate, but prevented the detachment of the desired material within the drill! And there it remains within the borehole, intact and still connected to the rock.