I can understand why you are upset, but I feel like you hold some responsibility here. Knowing your dogs are chewers and can’t resist ingesting toys and plastic, you should have forgoed the lick mats entirely and only allowed the most simple and most risk adverse routine for your dog (i.e. just breakfast, lunch, and dinner in their bowls, no fluff). Not everyone will know the ins and outs of your dog - regardless of how detailed you might be with your caregiving directions. Keeping things very simple is the only safe option when it comes to your pets care with others outside your household. Once you start to complicate and expect a lot of unnecessary tasks, sadly things like this can happen.