TF.N report:

"The Jedi robe worn by Sir Alec Guiness in Star Wars will be up for auction today by British firm Bonhams during a sale of movie and television costumes.

The robe went missing for nearly 30 years during which time it was used in other productions, such as The Mummy. It resurfaced during a stock check in 2005. Afterwards the robe was placed on display in London for a memorabilia exhibition."

Read the article here

UPDATE: "The BBC is reporting the final bid for the robe was 54,000 British pounds, which translates to approximately $105,000 US." (again, courtesy of TF.N)