Not a Moth

This little chappie was in my battery operated Skinner Trap at Linford Lakes Nature Reserve in North Bucks on 21st March along with a few moths, Hebrew Character, Clouded Drab and Shoulder Stripe.  It has had me vexed but I think it is an Alderfly and I reckon it to be Sialis lutaria.  Can anyone put me out of my misery/joy?   Is it unusual?   Apparently they are mostly aquatic coming out of the water to pupate and then emerge as the flying adult.  My trap needs a cable to be fed out from the base to the battery that I usually fill with a wine cork and I forgot the cork so entry could have been from there. There is an interesting story to be told of all that comes to a moth trap that is not Lepidoptera.