Hello DevinS,

Just running depreciation will not prevent the disposal of an asset in a prior period, since a disposal is just a calculation of depreciation with some different rules being enforced due to the disposal. You would have to have Period Close or Beginning Date information in the asset which would stop a calculation in a prior period. Please see How to clear Period Close information or How to reset depreciation on an individual asset or group of assets or maybe How to force prior accumulated depreciation to deal with the beginning information.

What appears on the GL Posting report is the current calculation, the Depreciation this Run, so there will not be an adjusting entry for this prior period disposal since you are really just calculating to a prior period and stopping the depreciation in that prior period. 

For the GL posting, there is the Disposal Report which will give you the Gain/Loss amounts for a given time period.