why don't they just repro their own experiment? If they can do it twice, then it isn't a fluke. at worst it's something specific to their lab. if they can't do it a second time, then the issue is settled.
I'm sure it will take a lot of time and money to run everything again. but all of earth seems willing to give them whatever resources they need.
It doesn't particularly matter if it is reproducible, as long as they have 1 working superconductor that they can hold in their hand (Room temperature/pressure), its a nobel prize. Other people can figure out how to reproduce it since it is clearly possible.
The challenge is proving they have even that 1 sample.
If it was some kind of fluke and is not easily reproducible but the sample exists and is a room-temperature super-conductor then it becomes a reverse engineering problem.
Considering the magnitude of the discovery and the relatively easy steps to reproduce the process, they would have to be outrageously lazy to have put the paper out without doing it a second time. In absence of a statement that they only tried it once, I think it's fair to assume they at least verified they can reproduce it locally.
I'm sure it will take a lot of time and money to run everything again. but all of earth seems willing to give them whatever resources they need.