Maybe it is a maintenance error, but thats a call to make on the day. If you're losing an engine because of, for example, oil leakage then perhaps you might attribute it to maintenance errors. We had a very near miss in the UK on a 737 not too long ago due to maintenance errors on both engines. If you've lost a single engine to a surge with no unexpected parameters then it is highly likely the problem is a traditional engine surge and confined to a single engine. The chances of FOD occuring to multiple engines on both sides of a wide body with an initial engine surge on one side and absolutely no other abnormal parameters on any other engine are remote. In this instance the crew assessed all the other engines and, with no abnormal indications, correctly assessed the remaining engines were fully servicable. We could all go into panic mode and land a quad immediately after an engine failure, but why not extend that to other systems? Perhaps after a failure of a single hydraulic system we should land ASAP in case a maintenance error deprives us of the remaining systems? What about a generator failure? Where do we draw the line?