Forgive me if you are already doing all this. Make sure you contact methodically all the pounds/Dog Wardens in a twenty/twenty five mile radius. Dog Wardens do not routinely share information on strays with neighbouring Councils and dogs don't know they have crossed a County line. Keep contacting them on a daily basis. Contact all greyhound/sighthound/all breed rescues in the area.
Don't forget to call the TRA, and the Highways Dept of the local Councils with a full description too, in case he was a road casualty. Even if chipped, many Councils won't automatically inform owners about deceased pets.
All vets surgeries - circulate poster/info/details in case he is brought in.
Contact things like Forestry Commission (if appropriate in your area), Country Parks etc.
Consider an appeal in your local media.
Frankie will almost certainly have a tattoo ID - make sure these details are circulated with the description, and whether he is chipped and neutered. Without knowing the details, do you think he was genuinely lost or was he stolen? Pointies are very desirable to certain sections of the community and can be stolen for coursing/working etc. If he has been stolen, contact a local sighthound rescue who will have probably have contacts in this world to see about a return (may need a hefty reward).
Good luck. Hope he is home soon.