The Modern Family co-stars were vacationing at The Mirage Las Vegas hotel on 14 July (12) when someone reportedly snatched Prokop's cash while they were swimming in the pool.
In a post on Twitter.com, he writes, "Gotta love getting robbed in Vegas... Thanks for the concern about the 1200$ it was stolen out of my wallet while we were in the pool".
The 21 year old had hoped the hotel's security team would be able to track down the perpetrator, however they had no such luck: "Wow the #mirage in Vegas sucks security team couldn't do anything lesson learned NEVER going back!"
Hyland was just as furious, tweeting, "You'd think a 'four diamond award winning resort' such as @TheMirageLV has security cameras to catch thieves. Won't ever be staying there."