Fabricating Your Evidence
This is smoking gun! The evidence that overturns everything we thought we knew! It doesn't have to be that radical - you can find a piece of evidence that people have never been able to unearth (like the Ark of the Covenant that Indiana Jones was looking for), but it might be easier to locate a missing map (or scrap of a map), a long diary your grandmother kept in her attic, or using technology - you may be able to find a detail in a photograph that had not been developed (on a pre-digital roll of film), let your imagination roam to think about possible evidence. This, again, rules out aliens and the supernatural.
You need to physically make the source, since you will need to present this in your final report. You need to make the fake evidence, and share a digital image/file of it in your submission.