Mobile home - No information held for

My father recently passed away, he left no will. I applied and was granted probate. He owned (leasehold) a mobile home on a park. I checked on here it comes up as "No information held". On the form AS1 it asks for a title number of the property, am i right in thinking i first need to use form FR1 to register the Mobile home. 

Oddly though he only lived in the house for about 4 years, when he purchased the mobile home surely it should have been registered then ? and if not does that mean i do not ? 

Andrew - mobile homes are not always registered separately so did you try the 'search by map' option?
What's the mobile home's address?

Andrew - many thanks. The site is registered under title EX772330 but the individual mobile homes are not individually registered. As I posted they rarely are as either their leases are 'mobile' so they don't own the land on which they are situated - they have a lease re the home but not the land itself
You need to read the terms of any lease/agreement he had with the site owner to see what can be done re ownership etc but that won't involve ourselves and therefore won't include a form AS1/registered title. I'd also suggest seeking legal advice as well