In truth, if you’re wearing a cap, a wig, and looking down, I’m not sure they could identify you at all.
Orr said authorities have video of a man in a black jacket on a cell phone, wearing a gray hoodie and a white baseball cap backwards placing a black bag at the second bomb site outside of the Forum restaurant on Boylston Street and then leaving the area before that explosion.
Orr said the man was on the phone at the second bomb site when the first bomb exploded.
Orr said the FBI looked at time man was on his cell phone and then went back and scanned all the calls made in the area to track who they wanted to talk to. http://boston.cbslocal.com/2013/04/17/cnn-boston-marathon-bombings-suspect-identified-in-surveillance-video/
That doesn’t sound very bright does it.
Using a phone to set off a device would certainly seem to be a big no no, if you don’t want your name on a list of people to check out.
Like you mention, even being on a phone at a sight would seem to cause you grief too.