Missing A Section of Landscape / Landscape Proxy - Don't think I deleted it - Any fix?

So I’ve been working on a landscape and suddenly a huge chunk of it has gone missing.

It looks like there are only 255 actors / components, however the landscape itself thinks there are 256.

I can’t find the proxy in the editor, or in world partition and have tried:

Disabling landscape streaming in project settings
Turning Nanite On / Off
Building Landscape
Building Nanite
Loading / Unloading world Partition

I’m ideally trying to hold off on building HLODs as it’s a long process and don’t believe this is the cause?

I’ve spent ages getting this to where I want it do be, so ideally would love to know if there is an obvious fix I’m missing or if i’m screwed or will have to start again.

Has this happened to anybody before? Would really appreciate some help.