I had to get the external hard drive and check the date to make sure it was correct. Yes, the time of year is correct and it was in my house on the cabinet door. However, I am not sure about the normal habits of ichneumon wasps but I do know this group is quite diverse. Ichneumons often use lepidoptera larva for hosts of their offspring. So I would think that as long as their are lepidoptera larva out or soon to appear, there will be ichneumons nearby as well.

So, if I take this (still have it) to an entomologist could they ID its species (by looking at mandibles under microscope or something)?

An entomologist who has training in taxonomy as a wasp expert and has the necessary keys MAY be able to distinguish this ichneumon wasp to species, but you need to keep in mind that there are thousands of species of ichneumons that have not even been discovered yet, let alone identified. In this particular case, some ichneumon wasps in the subfamily Ichneumoninae share similar characteristics to this one you photographed, but one would still need to see more details to confirm this.

I didn't realize this subfamily of wasps was so understudied (or mysterious) that they have so many unknown species in it. Thanks for the information, though I released it last Saturday because I wasn't sure if it could survive captive conditions.
Thanks,
Mark