I have same situation, My passport is in transit as per Blue Dart but on VFS Tracker it got changed to returned and undelivered message same as yours. When you receive your passport after getting this message ?I want to tell 1 thing my experience with vfs might help you guys
After the passport was stamped and despatched from vac back to my home after a day the vfs tracking changed to
"Passport undelivered returned to vac contact vac immediately "
When I contacted actually the passport was in transit to my home .
It was a technical glitch
If you encounter don't panic ,I said because I did ,I called vac they confirmed it was on transit and it was a technical glitch.