Recently–in the echo chamber that is Silicon Valley–several people told BoomTown quite separately that former Yahoo President Sue Decker had become an executive-in-residence at the Blackstone Group.

Actually, when reached via email, Decker told me she has yet to decide her next step after leaving Yahoo and had simply set up a no-strings-attached desk at the private equity firm’s San Francisco office, but is definitely not an EIR there.

And who says bloggers don’t check?

In fact, a move to join Blackstone formally would have been very ironic for Decker given that the firm–specifically, longtime friend and former colleague, Jill Greenthal–was one of the advisers to Microsoft (MSFT) in its failed takeover battle for Yahoo (YHOO), a fact that was highlighted in a post I did last year.

Instead, Decker has been keeping a low profile since she announced she was resigning from her post the very day new Yahoo CEO Carol Bartz arrived.

Decker was also a candidate for the top job, which she sought after sticking by former Yahoo CEO and co-founder Jerry Yang through some very rough times for both.

Her last day at Yahoo, after nine years there, was April 1.

In the email, Decker explained that she has not yet made any future work-related plans, but had simply taken up an offer from Blackstone’s President Tony James, as well as Greenthal, who suggested she could set up a small office there to attend to board work. The three all used to work together at Donaldson, Lufkin & Jenrette.

Even without an executive perch, Decker could use such a desk given that she sits on some very major boards, including Intel (INTC) and Berkshire Hathaway (BRK.A).

More than that, Decker–who sounded pretty happy to me–is not saying. Yet.

One of the more unusual situations in the current stand-off between Yahoo and Microsoft is the stress it has likely put on the longtime professional relationship and personal friendship between Yahoo President Sue Decker (pictured here) and Blackstone Group’s Jill Greenthal.

That’s because Greenthal (pictured here) is advising Microsoft on this deal, along with Chuck Cory and Paul Taubman of Morgan Stanley (who was actually Time Warner’s banker in its disastrous AOL deal).

Yahoo is being repped by Goldman Sachs, Lehman Brothers and Moelis & Company, an advisory boutique. All the firms on both sides stand to reap hundreds of millions in fees, if the deal is consummated.

Greenthal is a good pick for Microsoft to get the job done. She has a long-time knowledge of Yahoo, having worked with the company when she was at the Credit Suisse Group on the $1.45 billion purchase of Overture, one of Yahoo’s smarter purchases.

And her ties to Decker go back even further, when Greenthal was a banker at Donaldson, Lufkin & Jenrette. The pair worked together frequently at DLJ, where Decker was an analyst and research director before heading to Yahoo.

Back in 2003, in a BusinessWeek profile of Decker, Greenthal noted about Decker’s tenure at DLJ: “[Executives] didn’t always like her opinions of their company or industry, but they respected her.”

A source in Silicon Valley who knows both Decker and Greenthal said that the two have avoided speaking since the unsolicited Microsoft bid was launched by Microsoft CEO Steve Ballmer in an evening phone call to Yahoo CEO and Co-Founder Jerry Yang two weeks ago.

But one might also imagine their bond could also become a critical bridge in bringing the companies to finally make a deal, as many big shareholders are urging and Yahoo has been resisting.