I had a similar experience. My opponent sacrificed an artifact token to Darretti to get back their Dune Drifter. When the Dune Drifter entered (Not being cast) it was able to return their 5 CMC cost vehicle in the graveyard as well.

Not able to attach my log file because I am a mobile player and can't find it. In a recent Aetherdrift draft, my opponent won because he was able to use a Guidelight Pathmaker to search a Dune Drifter and reanimate a Riptide Gearhulk with X=0.

I ran into this vs Greasefang in Brawl. When Dune Drifter was reanimated by Greasefang, it was able to bring anything back from the yard

Same.

I had this happen to me as well, it was especially egregious since the Dune Drifter reanimated Salvation Engine, and unsurprisingly they won the match with that which I would probably have won otherwise :( I also had the impression that this person knew that it was bugged and was abusing it.

I had this same error: Guidelight Pathmaker -> dune drifter -> rangers refueler.

Faced the same bug with Dune Drifter being reanimated by Tune Up, then reanimating a 7 mana creature though X should be 0

Sparky Repro

I wanted to add that this is everytime Dune Drifter gets reanimated. I reproduced this with sparky (attachment didn't upload and now I can't edit ...)

Same issue as poster.
Guidelight Pathmaker choosing to put Dune Drifter into play can select any card in graveyard regardless of X cost. This issue can be replicated with any creature in graveyard.

Commenting to say I had this issue as well, and it seemed as though my opponent did it knowingly so are there already people abusing this?