Glad to hear that the issue is resolved.
Sounds like the librarian was a real 'jobsworth'.
I had a similar issue a couple of weeks ago when I wanted to send a packet by Royal Mail, recorded delivery.
The assistant weighed the packet and told me the charge, and I asked could I pay with some postage stamps I already had.
She said I couldn't use them as they used special recorded delivery stamps.
I was dog-walking and never take out cash, when I explained, she did allow me to use the stamps in my pocket.
Have never come across this before, and no assistants have asked since. But I thought that this particular assistant was going a bit over the top.