I received one of these and it meant a lot to me.

It would be weird if a group of my close friends or family members did that but not coworkers.

I guess its a way of your coworkers acknowledging your loss without actually having to talk about it.

For me, when I lose a loved one, the last thing I want to do is discuss it at work as it just makes me want to cry. Knowing that others are aware and sensitive to it, just helps me try to get past it.