Upon realizing just what the package was, Lucy had quickly shut herself in her room to get properly attired, which was to say: cargo pants and a slouch bag for extra ammo, along with a strap for the gun, just in case she needed her hands for something, because it would be just like Peter to leave her flag somewhere only she or Diego -via parkour- or Five -via powers- could get at it.

She was also a little surprised by the revocation of the usual 'no powers' rule, though figured it was because most of them were adults with arguably better control over their powers than they'd had the last time they played this game.

Once she'd wrangled her hair under a bandanna she was ready to go, kicking off her shoes and taking a moment to listen for any noise in the hall before opening her door just far enough to get through it, watching out for the three creaky spots in the floor between her and the stairs, and heading upstairs instead of down, planning on checking the upper floors for her flag first and working her way down.

The best places to catch her are probably in the library, probably on top of or wedged between shelves.
The Living Room, probably up in Grace's gallery, hidden behind the bar, or under furniture.
The Kitchen, camping out to peg people before they can get their flags hung, hidden in among the glass display cases, or just getting a snack, gotta keep fueled after all.