You drove your Peterbilt truck through a truck wash with your gas cap off should you be worried?

First off, if you're driving a truck, and calling it a "gas cap", something is a bit awry here. Although lots of entry level companies have Peterbilts in their fleet now (such as Werner, JBS, TMC, even Swift has a couple), so I shouldn't be surprised.

The simple answer - YES, you should be worried. That was a very careless thing to do, and you'll probably need to have your fuel system drained out now.