see suiteanswers 69197 - looks like this changed in 2019.2 (IMO this is an insane change) - the alternative they offer is to use the Depreciation Monthly Report from the FAM suite of reports.
Posting reference is the field that gets populated when you view depreciation history records on an asset, but that is blank in a saved search.
Apologies when I looked at the FAM depreciation history I was looking at disposal records which had a depreciation component