"Happy to skip the party to inspect your bower and be, mm, the most impressed of the bowerbirds."

"I think Julie might object," Bruce says, raising an eyebrow. "To both our disappearance and to you in particular."

"I'm very objectionable."

"I wouldn't want her to worry."

"Wise of you."

He stands up and starts walking away.

Introductions and small talk(?) achieved, Bruce wanders off again, to the next rich socialites he really ought to actually meet.

A few days later--

Barry Allen is having a good day. 

He has a few dozen deliveries to make across Central City off various gig economy apps. He has a couple of TaskRabbit tasks from people who don't expect to actually watch him do it; he assembles furniture, cleans a house, fetches someone's dry cleaning, and fixes a toilet. And about ten minutes after he begins work, he's done for the day and can go back to his apartment and read comics. 

If he's still in super-speed mode when night falls, he'll get a few dozen more chances than most people to look up and notice there's something amiss. An open window he didn't open. Shadows falling oddly, shifting when they shouldn't. It takes a relative eternity to cross this room; if at any point he were to just turn around, he might catch his intruder mid-skulk.

Instead, of course, he's going to have a mild heart attack.

"You stopped that robbery," says a voice behind him, deep and raspy and inhuman. It waits until he's finished the issue he's on to say this. It's a considerate nightmare voice.

When you're sped up, it's hard to understand human speech, but the deep raspy nightmare voice is not less startling for that. He accidentally speeds up to country-crossing speed and then slows down to normal human and catches all of the horrible nightmare voice's sentence.

"Why the fuck are you in my house?"

(Barry talks fast, even when he's not sped up.)