a bot accessed a hidden url

I'm learning real fast from these snippets.
The page was not much more than a skeleton to check responses from the controller so no tracking scripts were involved.

I suspect it is internet explorer (on win 7) because, although google is the default search engine, bing is the only engine to have tried the url (every night since then!) and I ran multiple tests of the url in all the other browsers (on linux and apple) as well and none of their search engines tried the url.
However, another possibility which came to mind in the meantime is that the win 7 installation has mcafee antivirus with the safesite feature enabled and this of course would mean that all requests go via mcafee which makes for another possible leakage point.

I find it amazing that a url which was only used probably about 20 times in the space of a few hours could be seen by a search engine as "interesting". These search engines must lead extremely boring lives!
Well, fortunately I've learned my lesson before it's too late.
Many thanks for the tips.
Bill