Migrants and a partially good bird

This morning was another great day for migrants here (for mid-August). I had three warb sps giving flight calls between 7:00 and 8:00, one of which was most likely dendroica from the more buzzy zeet (but I'm not about to start calling my BTBW's online and get called out by Bill Evans like somebody on here...cough Putter). Also had a female/imm PUMA flyover the pond, a Bank Swallow was associating with the BARS, and a four-ship of "pinking" Bobolink that went over fairly low. I had given up on the pond action and was shifting to the trees on the edge when I saw a small white egret drop on the pond through the trees. I caught glimpses of it through the trees and got the following field marks:
1) Small, flew right by a DCCO and was smaller or comparable to it in both body size and wingspan.
2) Very nondescript legs, nothing stood out and they just sort of blended into the bird and the background (ie no contrasting foot color).
3) An almost dusky appearance that wasn't the pure white of adult SNEGs or GREGs.
4) I saw it with it's neck outstretched (very crane-like) and it's neck length was far too long for CAEG to be a possibility.
I didn't see the beak color, beak length, or wingtip color. I feel I can safely rule out CAEG, adult SNEG and I'm left with immature LBHE and immature SNEG. Unfortunately I was unable to relocate the bird in question once I got to a better vantage point on the pond and I was already late for work...
I spent my lunch break and the hour following work searching nearby ponds and habitat without any luck relocating the small white heron of interest (although I did have 4 other heron/egret species while searching).
The searching wasn't in vain however as I heard a bill snap and was attracted to a dashing looking Philly Vireo in one of the willows surrounding the pond. And then a Traill's Flycatcher showed up as well. A flyover SOSA rounds out the migrants for the day (PUMA, BANS, BOBO, PHVI, TRFL, and SOSA).
I will continue to keep looking for this egret...while it's cool, it will be far cooler when I know exactly what it is... And either would be an IL bird for me...and we all know eBird doesn't count sp ticks...