Ivomec is ivermectin. I don't understand why the vet would use both.
Did he at any time take Dumpling out of the room you were in? If not, then I think you would know if he was injected. Both the Ivermectin and the Revolution doses may have been in a syringe which was put against the skin. The picture is impossible to tell if there was a needle on the syringe but he is not curled up so I doubt it was a needle.
You mention he gave you Ivomec for cleaning the cage? Is it on the receipt?
* * * Nancy * * *
Retired from breeding
Rescue contact for both the Hedgehog Welfare Society and the IHA
Rescued over 70 (and counting) hedgehogs needing a new home