I woul cut back 2/3, replant propperly and make sure it is planted at the right depth.

Soak,
perhaps put up some umbrella or other shade screen.

What zone are you in, does it get hot now?

With some luck it will recover, regrow and bloom somewhat later and should be fine for next season.

So, good luck, and perhaps you have to kick your roommate into some sensitive area to make him listen...

Bye, Lin

I would not cut it back but just keep it watered and it will recover in a week or so. Worst case would be that some of the foliage will die and it will sprout from lower down on the plant. There is plenty of time for it to catch up with other plants.

I planted an already started in a pot tuber with 2 few-inch sprouts on it a few weeks ago, made a mental note to label it and then walked away and got distracted as I often do. A few days later I stepped on it walking through the bed, ugh, I was so mad at myself! Well the 2 stems broke so I just snapped them off and figured that the thing would hopefully recover and worst was that it would lag a bit behind it's partner/companion dahlia in growth since it had to start from scratch.

I was so surprised when the other day I noticed it has THREE new sprouts coming up and they are almost as tall as the other one which didn't experience a break! It is almost like the thing did better because the sprouts broke off...interesting for sure. If I was brave I'd try it with others lol.

So you may be pleasantly surprised if you do break off the sprout, here's hoping for you!