It is not uncommon, when removing the front wheel on Comfort or Adventure strollers, to accidentally push the push buttons into the frame.
If you don't remove the front wheel from the frame, this won't happen to you.
Not to worry, you can put the studs back in place yourself!
With a hook, such as a crochet hook, bent tent peg or something similar, you'll have the push-button clip out in no time.
Slide your hook into the frame and position it behind the push-button clip. You can now pull the clip out of the frame. You might need a few minutes of fiddling, but eventually you will succeed.