Beyond the information security risk around the loss of this specific device, what really worries me is the physical security implications here. I'm certainly no expert on the subject, but it seems to me like, in a building like the US Capitol, it should not be anywhere near this easy for unauthorized people to waltz into an office or conference room in the first place. Let alone walk away with items from within that…
To prevent unauthorized entry, Capitol Police would have had to put up a fight. Seems they were unwilling to do so. If America continues down this path Russia (and others) are just gonna have a field day.
At my own workplace, all the areas that are not intended for public use - office blocks and most meeting rooms, for example - are locked at all times and have keycard access. Defense in depth, y'know? And we're not even a juicy target like the US Capitol, we're just some company.