Hi
For future reference
If you pre install Prey it may be able to ring home, but if HDD errased Prey will not help
Some Dell laptops (and some other companies) have a BIOS /UEFI with option to run equivalent to Prey which can survive the HDD being erased
https
/preyproject.com/
Report to Local Police and ask about about suspicious local shops selling second hand laptops and go for a look round your self
Do you have serial number of laptop (or HDD) ?
(If not difficult to prove ownership after HDD erased)
Finally was it stolen or did you leave it behind on bus,
(if left behind ask bus company if it has been found)
regards
Mike Barnes