Matt Thompson was heartsick when he discovered that his beloved Sally Ann had left his Glendale, Ariz., hotel in the arms of another man.

They had been together since 2003, and Sally Ann was something special. Irreplaceable, perhaps. Thompson was on a three-week road trip when she disappeared, the hotel room door left ajar.

Maybe you'd have to be a poet or a songwriter to understand Thompson's bond with Sally Ann, however. She was his custom-made mandolin, and he was on tour with the Minnesota bluegrass band Monroe Crossing (Thompson, Derek Johnson, Lisa Fuglie, Mark Anderson and David Robinson).

Thompson and band members had gone to a movie before their evening show when a thief broke into the room and stole the mandolin and a fiddle and bow, Thompson's prized possessions and source of his livelihood. The mandolin had been made by Lloyd LaPlant, a custom instrument maker in Grand Rapids, Minn.

When he saw the open door, "I immediately thought about my instruments. I looked inside and they were gone and my heart just sunk. I was in shock," Thompson told a TV station in Arizona.

The band posted news of the theft on its Facebook page and other social media (www.monroecrossing.com) as well as on websites of bluegrass publications. News spread in the music community by social media, and soon musicians and fans were calling pawnshops and searching Craigslist and eBay for any sign of the instruments.

The bluegrass community was as outraged as a bluegrass community could get.

"Boo and hiss," someone wrote on the band's Facebook page.

"It was a pretty big deal," said Art Blackburn, the band's booking agent. "The mandolin is very special to Matt."

Not to mention worth a few thousand dollars.

Monroe Crossing happened to be scheduled to play a benefit for an agency that pays for dental work for those who can't afford it in Texas, so maybe a little karma was in order, however.

The next day, a musician named Jerry saw a man trying to sell a mandolin in a gas station lot. Jerry's son wanted to learn to play the mandolin, so Jerry offered $300 for the instrument. Jerry then went home to look it up on the Internet. That's when he found mentions of the theft. He called Thompson, then brought the mandolin to the band in the middle of a gig they were playing.

Thompson had told the crowd about the theft, so when Jerry walked in with Sally Ann, the place erupted.

"It made a bad incident better," said Blackburn. "It made the rest of the trip a little easier."

Unfortunately, the fiddle is till missing, along with Thompson's e-reader.

Thompson, "the voice of Monroe Crossing," has been a mainstay in the local bluegrass scene for many years, from winning a Minnesota State Fair contest to playing on Garrison Keillor's "A Prairie Home Companion."

Fiddle or no fiddle, Monroe Crossing's shows have been getting rave reviews across the South and Southwest, as has their 13th CD, "The Road Has No End," inspired by road trips like the one they're on. I'm guessing the next CD will feature a song about a missing mandolin.

The road may not have an end, but as it turns out, it does have a partially happy ending.

jtevlin@startribune.com 612-673-1702