Hubpages sticks a noindex tag on newly-published hubs ("Pending"). Pending status stays for about 24 hours (and resets the timer if you edit, so don't touch it after you hit publish). Your Dashboard indicates Pending hubs with spinning arrows, then switches the icon to an H once they're featured and the noindex tag is removed.
If a search engine sees the noindex tag on a Pending hub, that tag is telling it, "Do not index this page." It may then take some time --sometimes weeks-- for the search engine to return and check again to see if you want it indexed, after all.
So what probably happened is that Google crawled your page quickly while the noindex tag was there, and therefore did not index it, whereas Bing and Yahoo straggled in later, after the tag was removed. (That, or they bend the rules and ignore it when people request that they not index a website.)
This Pending hubs policy was implemented at the end of August. Browse the official announcements forum for a little more info on them.