I don't see how one can replicate the original welding conditions if the nonessential variables such as voltage, amperage, travel speed, and interpass temperature were not recorded on the PQR.
If the nonessential variables listed above were recorded for each weld bead, then I would venture to say you could weld a coupon and measure the hardness if you client agrees to the proposition. The same welding parameters would need to be used to produce that same cooling rates.
Just my opinion.
Al