I'll bet you're right. FWIW, all leave has been canceled for the 420K federal employees (myself included) who are working without pay -- meaning that all vacations, pre-approved or not, are canceled. We've been told that if we attempt to take any kind of leave at all -- even a single day for bereavement or a medical emergency -- we risk our status being changed to "furloughed" and losing the right to back pay. Even if that wasn't the case and we were allowed to take vacations, nobody I work with can afford to travel right now: not when we're trying to keep every penny in reserve to pay for our medical insurance (most of us carry the medical insurance for our entire families thanks to the fact that the government contributes a portion of the premiums, but now we're on the hook for the whole premium amount unless we want our coverage to lapse), mortgages, gas and vehicle maintenance, etc., for who-knows-how-long.
I still haven't told my 10 and 12-year-olds that our long-planned-and-already-paid-for February break vacation to Universal will also be canceled if the shutdown continues into mid-February, because I won't be able to go, and because the refunded hotel costs might help keep our health insurance going for one more month. I'm just praying that the government will be reopened before then.