1993 Mercury Cougar A/C cool not cold after running with l

The A/C was recently switched over from R12 to R134 and the compressor was replaced with a new one. It was working good and cold until this morning.

I drove it this morning with the intent of defrosting the front window so the heat/cool lever was in the hot position while the A/C max switch was pushed on. I didn't notice this until this afternoon. Now the problem is that the air only blows cool (barely) and will not get cold.

Did I damage something by running the A/C in this manner? What can I do? Did I cause a leak of freon from the system by running it this way? Would putting in more freon work?
(the car was repaired only 3 weeks ago but the repair was done out of state so I'm unable to bring it back to the original repair location).

Thanks for your help.