Can a condo interior room walls have steel studs that are paper thin?
Even though you found the stud with your stud finder, you may have missed it. Even steel studs will offer a bit of resistance to drilling, and you should see some metal filings or twists following the bit out of the wall. You may have to try again with a very small bit 3/4 inch one way or the other to find the stud. Use your stud finder to give yourself a better idea what side of the original hole you should try.  Of course, you can use the hole you already drilled by inserting a drywall anchor rated for the load you want to attach. I prefer the corkscrew type anchors to the expansion type.

There is a difference between the interior private walls and the common wall in condos. Common walls are always thicker, usually thicker sheetrock or two layers of 1/2 inch rock. This is for a longer fire time rating and soundproofing between units.