I wasn't attacked at the time (I've sent print screen to bug email) and even if I was, there's no way I could have lost that much SE.
I only had one tab open and I attacked 3 characters from the duel page with middle mouse button, within maybe 2-3 secconds. I was able to do that because I was using firefox. When using IE, when I click middle button to attack, jscript pop-up screen asks me if I'm sure.
The tab of the first battle showed my SE won from EH (and on the left I saw total SE). The seccond tab showed the same - which means it showed my 47k sum. I no longer remember if on the third tab there was 49-50k, or it was 20something. In any case, when I went back to my profile page (and I did that from the tab of the seccond battle I believe), my 27k won from that battle were lost.
I'm not sure you'll be able to reproduce the bug as I have been attacking like that for 2 years now, and this is the first time it happened (well, maybe it happened some other time but it was small ammount of SE so I didn't notice) but as quint had the same problem, seems it's a legit bug.
In any case, I want my 27k back!
If you need more info, you can also write/ask on my email
PS - sadly I no longer have those battle reports on my previous battle page, hope you did not delete them