Megadeth Singer's Mother-in-Law Is Missing Sally Estabrook has Alzheimer's, last seen Saturday By Evann Gastaldo, Newser Staff Posted Oct 7, 2014 10:22 AM CDT 12 comments Comments Dave Mustaine of Megadeth performs in concert in La Paz, Bolivia, Friday Nov. 25, 2011. (AP Photo/Juan Karita) (Newser) – Megadeth frontman Dave Mustaine's mother-in-law has gone missing from a San Diego-area campground. Sally Estabrook, 75, has Alzheimer's, and was last seen around 4pm Saturday at the Pinezanita RV Park & Campgrounds in Julian. Her husband says he got out of the shower to find her gone, NBC San Diego reports; it's presumed she wandered off, ABC 10 reports. The search for Estabrook widened yesterday, with officials worried about her safety due to the hot weather and the canyons in the area. No trace of Estabrook was found at the campground, so searchers expanded the perimeters to about five miles from where she was last seen. Mustaine, who grew up in the San Diego area, was at the search site yesterday and also tweeted asking for prayers and "good thoughts" for his wife; his daughter Electra tweeted asking for help finding "my beloved nana."