I didn't read the rest of the post because after you wrote "bike rack" I knew something bad was going to happen. There are so many bike rack horror stories on this forum. You're lucky they didn't do more damage because bike racks are just bad news. About 75 years ago, bike racks were a good idea where one could safely lock their bikes. Not anymore. Today, you must find a spot far where others are not likely to steal your bicycle. In other words, hide the bike.

If you keep putting your bike on that rack they'll come back with some industrial tool that will brake your main lock! Or they might decide to just vandalize the bike from top to bottom just for the fun of it. You can no longer use that rack because the person who did this may very well do it again but worse.