Bobby was not blind.
Therefore he had of course noticed that Marie was wearing the tag Logan had given her when she slept. He didn't like it -- but what was he supposed to do, rip them off and get into a huge fight?
Logan was not there, after all.
But then he came back, and Bobby had to see Marie practically running to greet him. He followed and watched his untouchable girlfriend hug the man Bobby had spent a lot of time trying not to think of.
When he watched closely, he could almost see what Marie saw in Logan.