Hey ICU,
Not 100% sure it's too late for you. I think you can still dry hop it, here's what i'd do:
Pull keg from fridge and put back into basement, let gas out, and pop keg open add the dry hops in pantyhose or whatever method you use, add a bit of gas back in to purge air, but not necessarily to bring it up to your desired serving CO2 levels. Let sit min. of a week, more if you can. Then pull pantyhose once time has elapsed, and cool back down to serving temp. I don't think the temp swing will cause you any issues, you should be ok.
Hope this helps.
Cheers.