[Maggie-May24]

They've refused me because my passport left the country in between but was never asked to submit more information or payslips to prove I had actually completed it.

Wasn't that required as part of the application? AFAIK, you need to provide the evidence that you've completed the required work. They often don't ask for more information, it's incumbent on the applicant to provide everything that's needed for them to make a decision.