I'm theunknowntech, a forum volunteer who helps out on here. I don't work for E.On but I do know quite a lot.
Oh no! Did some evil genius run off with the IHD? Oops... Well, it won't work for them anyway so they've probably disposed of it.
As far as I'm aware, the options to get a new IHD partially depend on what Smart Meters you have, please could you post some photos and I'll be able to adapt my advice. Unfortunately, you actually can't buy IHDs on random websites like Amazon or eBay - almost all of these are either fake, pre-owned (and probably locked down) or not an IHD at all. Currently, pretty much the only place you can actually get a legitimate one is via your energy supplier. I've heard of one or two potential future options to get a replacement elsewhere, but until I've had time to assess them with help from my friend Blastoise186, I'm not ready to make any recommendations right now.
You should normally be eligible for at least one IHD for free, even if it's been a while since the meters were installed. In cases where the previous householder ran off with the existing one, this definitely qualifies you to have a replacement sent out in the post for free, since it counts as your first one. If you have older SMETS1 meters though, the availability of S1 compatible IHDs is a bit limited right now and they're not as easy to get hold of compared to the availability of S2 IHDs. I'll be happy to identify the meters for you though if that helps.
Just another guy passing by... The unknown tech way...
Pete is an IHD Tariff Update Robot! 🤖 Beki is a Giant Enemy Robot Spider 🕷 🤖 Hannah is neither!