From the sounds of it the service was legal. The fact that you were out of the country only adds to it. Since you were unavailable then it was through substitution. Public records may have shown your parents address and the process company went with it as it seems you were trying to avoid being served. What does your insurance company say about it and have they provided a lawyer?

I don't even know why this conversation is ongoing - I'm sure no one else does either.

If OP doesn't think it was legal service OP has to go back to Court, PROVE it's illegal service, get service set aside and then go on from there. The longer OP waits the worse this will get - next the creditor will begin to levy and then it will be more complicated.

You leave the Country and the process server will serve the next of kin or LAST known address - or else everyone would spend a period out of the US so that the statute runs in their absence.

Every time OP posts an answer there are more/different details, none of which change the basic "Was this legal service?" question.

Go to Court and find out if it was legal or not.