Had the same problem 2 years back. Bought a deal and paid twice although the deal was only available once.
Contacted support, gave a detailed description what happened, a time stamp is important.
They acknowledged that there was an error and contacted Google for me and got the money back after around 2 weeks. (the support is not the fastest but it works)
If someone goes the other way round its clear that there will be problems. I don’t think Sg checks automatically if there was a bug. This seems to happen really, really seldom haven’t heard it beside mine problem, so Sg probably just see the cancelation of the deal and takes the gems/mats back.
I made the experience that the support, although slow, most of the time works just fine. So I hope that if you tell them exactly what happened and ask them to look into your buy history that it will get resolved.
And although it can get tiresome, always stay polite, works better than yelling at them although sometimes you just want too 