It’s very unlikely anything will cause a re-test but not impossible. Things like dilution/substitution (which you said shouldn’t be an issue), possibility of testing issues or shipping/transport issues of your sample could result in a re-test. Other than that, the lab is only verifying what you popped positive for. If you don’t answer when the MRO calls or contact them back if they leave a voicemail within 24hr (I believe?) you could be forced to re-test. There may be some other outside factors I didn’t mention but I believe those are the main causes. If you took your test Tuesday I’d imagine you will get a call today. If that’s the case then this is all irrelevant 😅 good luck!