Need an appraisers eye on a cash out refi

[Bobby Andrews]

Just completed a down to the studs rehab on a ~1300 sq ft property in Indiana. We pulled separate permits for the ~1300 sq ft house and the 400 sq ft 1 bed 1 bath detached garage conversion in the back. The appraiser made no mention of the rear unit on the appraisal so we submitted a ROV. Then we got that back with no adjustment at all to the appraised value but still no mention at all of the rear unit. I know conversions or extra space like this are sometimes valued differently than if it were part of the GLA but it seems inaccurate to assign zero value.

For context, I've done several BRRRRs in this market and the price per square ft of our completed refinances are all very similar to the price per sq ft of the ~1300 sq ft front unit. If they somehow included that rear unit in their valuation, that would mean the whole property ppsqft is like 25% less than our other nearly identical properties (completed in the past few months as well) with no outlying differentiators. 

I haven't had an issue like this before so I'm trying to figure out what to do. Thanks!