Unreferenced RMA Receipt is NOT getting Costed

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we are receiving Unreferenced RMA (without referring to Original Sales Order). Costing is NOT happening and it shows below message.

The incoming inventory transaction could not be costed because an existing layer cost was not found to use as the actual cost of the item.

Cost Profile has set up as
Receipt without cost=Use First Receipt Layer Cost.

when we are receiving then we are creating a new Lot and Our Valuation Unit is the combination of Cost Org-Inv Org-Lot.
Please suggest what will be the right way so that Unreferenced RMA Receipt can be costed.