I've worked in (non-automotive) service in the past and people make mistakes, especially when under pressure from management to get S*** done etc.
From their side of things, they can't really fix something unless they know about it.
Heck I've dealt with quite a few workshops over the years and from time to time even the good ones make a mistake (leaving engine bay trim loose, not tightening caps, forgetting to reinstall centercaps on wheels when changing tyres... just as a few examples). After mentioning it to the workshop manager or owner I got an apology and the problem/s resolved in a quick manner with no charges.
The least you can do as a customer/client (paying or non-paying) is to bring issues to the attention of the business so they have a chance to resolve it.
In saying all that, I do agree that they did a terrible job and potentially caused irreparable damage to some of your interior which would leave me fuming also.
However it's handled, I hope you get an apology and they repair/replace any damaged components at no cost to you.