At my Grandmother's funeral my half-brother who had never been in a Catholic Church in his life decided to go to communion. Why? Just because. His only "church" experience was to be baptized during vacation bible school in the 7th grade.
It happens more than you think. People don't want to look left out. Others don't think it's a big deal.
yes it does, unfortunately. A noncatholic I know dismmised it as snobbery@@ I told her I have more respect for other's faith and if something was inclusive to only Protestants in part of a service, I would honor that.
You're right, as an honest mistake it's no big deal. It is a big deal when you use the situation in a commercial venture to mock Catholics and their church.