As already explained, a very simple, proper magnetic measurement of the susceptibility is required, AC and DC susceptibility.
In a localized domain superconductor the bulk material could have a combination of superconduction and semiconductor junctions. That's going to be tricky to measure magnetically.
Yeah, that's pretty what I suspect.
There may very well be a superconducting compound in the sample but it's so heavily mixed up with other things that measuring it and getting results to conclusively identify superconductivity is extremely hard.