Area C / ZTL fine (Milan)

Hoping you can help me with an Area C fine I've recently received.

Yesterday a letter from nivi ,who I think collect fines on behalf of Milan, turned up. The infraction is dated as 14/Jan/ Protected content the date of ascertainment 12/03/2014. I saw somewhere on the net (now lost and unofficial anyway) that said theres a time limit on these fines of one year, if they don't notify you within a year you don't need to pay them. Anyone know anything about this?

As it occurred 15 months ago I have literally no idea if I rented a car on that day nor who was driving it (it could have been me or my girlfriend).

It also says "the present notice is not a notice of violation and therefore cannot be appealed" which sounds incredibly unfair. Although, it's not like I could do much appealing anyway given they're telling me 15 months later.

Cheers

Andy