30 minutes is a long time to wait, but what you could do instead of acting like a four year old is:
1. Consider why it is taking so long. They are probably busy and trying to get to you as soon as possible.
2. If you don’t want to wait any longer, go somewhere else.
3. If they’re clearly just dicking around and ignoring you (which is really highly unlikely) actually confront them verbally, or again, just go somewhere else.
What fucking adult writes on a table with ketchup?
And now someone else gets to wait 45 minutes because someone has to clean this up instead of helping them.