13.96V is a tad low, not ideal but should be enough to charge a Battery, 38% Battery is telling someone the Battery is not fully charged or could be a Battery issue, difficult to tell unless you fully charge the Battery, give it a chance to recover and then test it again. Bit like saying 'oh, your tyres flat mate, going to need a new one', rather than putting air in the Tyre and so whats going on.
What he should have done after fitting a good fully charged Battery is test the charging voltage again, my money would be on if it was reading 13.96 with a flat battery, would probably read 14+v with a good battery.
Unfortunately, the deed has been done now, so unless they've giving you your old battery back, guessing not, as they get around 15 to 20 quid to scrap a battery, your never know, just need to check or keep an eye on your charging system.
I would put that down to, taking a flat battery in to be tested, only to be told its furbed, need a new one.