Peru is investigating claims that a beauty pageant contestant was lured to Gabon to become the lover of its 67-year-old president, Omar Bongo, and was stranded for nearly two weeks after she refused. A spokesman for Mr. Bongo said he was unaware of the allegations. The Peruvian Foreign Ministry said that Ivette Santa Maria, a 22-year-old Miss Peru America contestant, was invited to Gabon to be a hostess for a pageant there. In an interview, Ms. Santa Maria said that she was taken to Mr. Bongo's presidential palace hours after her Jan. 19 arrival and that as he joined her, ''he pressed a button and some sliding doors opened, revealing a large bed.'' She said, ''I told him I was not a prostitute, that I was a Miss Peru.'' She fled and guards offered to drive her to a hotel. Without money to pay the bill, however, she was stranded in Gabon for 12 days until international women's groups and others intervened.