A lot of online plumbing shops probably have a customer service department. I'd recommend you email them, or call or use the chat feature online if they have one since you haven't gotten many replies here. Occasionally a plumbing expert will weigh in at Houzz, but posting on a dedicated plumbing forum or asking a supplier directly may be a more direct route to your answer. Even if the handle was broken off, I'm not sure you can replace just the handle. There might be more to it than that. Too bad you didn't have documentation of the workers negligence that probably led to this so you could get the decking contractor to fix the damage.

Put the handle on and see if it works, if not cut the pipe inside and pill the old one out and install a new one. If needed use a frost-proof spigot.

Hard to be sure from the photo, but it looks as if some over-enthusiastic worker snapped it off. If there's a screw in the center, you may be able to remove the broken off stub and replace it with a generic control.

This is a Woodford Model 20 outdoor faucet?

Woodford Troubleshooting

Note that there is a 1-800 # at the link. I would call Woodford if a generic replacement handle & screw doesn't work.

This looks to be an older Woodford faucet that has had the valve stem broken off. It looks similar to this current model:

https://www.woodfordmfg.com/woodford/Wall_Faucet_Pages/Model-27.html

These valves are high quality and rebuildable from the outside. If you talk with the Woodford folks it is very likely that they can supply the inner valve assembly (parts 1-10 in the exploded view) to put the faucet back in working order.