Actually, that's a common misconception. Icy units won't thaw by themselves when they're frozen like that for weeks because it's too cold outside. The best way to thaw it would be to turn the A/C on and hopefully there is enough refrigerant in the system to thaw the condenser
This is EXACTLY why I put a cover and lock on the thermostat in my last office. lol lol I did it because in in my first office, this is what I had to deal with on a Monday...and a HOT one at that. I learned a valuable lesson, or er, was taught a valuable lesson.