Real estate investor Marjorie Oster was pleased when she snagged what looked like a good deal through a Miami-Dade County foreclosure court auction: a four-bedroom house in Cutler Bay, with a swimming pool, for about $95,000. But when her husband drove by the next day to check on the property, he saw “someone cleaning the pool, a lawn service cutting the grass and a note it was being tented for termites,” said Oster, a Miami resident who has been in real estate for 15 years. It turns out the house she thought she had purchased had been sold in a short sale the week before to someone else — Osberto Jimenez, a 40-year-old Cuban-born truck driver. The law firm handling the foreclosure for the lender mishandled the paperwork and never canceled the auction sale….