this is okay if this is the only basking light you have --- if you have a regular solid bright white bulb use that and shut that one off -- you can use the outside sun for UVB till the other one comes in - he will be fine a few days w/ out UVB --- its long periods of time you dont want to do that
Before leaving the store make sure you take a good look. I was also originally purchasing mines from there but ended up buying online. But On here and another bearded dragon I’m on people who purchased from them and Petco have discovered issues. One owner beardie passed after 2days of having him home, another had tail rot, another was missing a toe. So all in all just be careful and examine well.