Shy girl,
You need to go to the gPS, tell them that you are having to use someone elses meds (that should ring alarm bells) and refuse to leave withoit a pare prescription in your hand..Take a book though as it may take a while! Don;t blame them, but explain that you have now been without lifesaving medication for X days, and they need t ohelp you sort it out.
OK, it is their fault, but to be honest, the important thing is to get your medication. Also, if possible, explain to them that you will be reordering 3 weeks beofre teh old stuff runs out, so that you don't have to camp put in the gps reception again! I am more than happy to shout if I need to to (so not a shygirl!) but it doesn't always work...in this instance, I would go for teh appealing for help approach...leave the blame out of it, what you need is a result.
I have only had an issue like this once, and that was becasue the insulin manufacturere had problemsm abd wasn't producing any insulin. I went back to the GP in a panic...and pleaded with them to help and they did.