Thanks Mediabandit, that's what I was thinking, but I just wanted to clarify.
jmitch, please let us know if you meant differently, but if this is the case, and you really cannot dismantle the UVB source, then from what I understand, a bearded dragon can go without a UVB source for a while (a couple of weeks), though it's best (except under the conditions mentioned before) to always have a UVB source going for your bearded dragon, if possible.
An alternative is to make use of natural sunlight's UVB, and it's possible that your friend could take out your bearded dragon for some natural sunlight daily, but I wouldn't risk that unless your friend is experienced with bearded dragons, knows what they're doing, and uses a harness of some sort to prevent any potential escapes. Otherwise, if you really have no options, your bearded dragon can do without a UVB source for the week (though again, not recommended).