Did you/he retorque the head bolts after the car had been run from completely cold to full operating temp several times? Failure to do so could account for the lose of clamping force. Also, failure to chase the threads in the block could create a false torque reading which would only be revealed with measuring the breakaway torque.
Anyway about it it doesn't look like it was leaking bad or very long. Measure the block to make sure it's flat (same for the head), clean the crap out of it and install a new HG. You may want to get the head vacuum tested and UV inspected for cracks while it's out too.
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