Normally, the Volvo Cars app lets me unlock the car.
This is also true for the version installed on the Apple Watch.

The other day, we were planning to go into the lake. I left my key fob and my iPhone in the trunk of the car and locked it with the Apple Watch. We ended up not going into the lake and came back to the car a few minutes later. The app on the Apple Watch was in a weird state. It didn't have an "unlock" button. I was going to panic because the car was completely locked.
Fortunately, someone lent me their phone. I was able to call Volvo Road Side assistance and they unlocked the car for me.

Has anyone ever experienced the loss of the "Unlock" button on their Apple Watch?

Thank you