The mother of a Plainfield man missing for more than a month now said she believes he is still alive, despite a life-threatening medical condition.Morgan Johnson, 27, was last seen at 11:45 p.m. May 18 leaving the Value Place hotel at 6295 Gateway Blvd. He lived at the hotel and worked at nearby Brightpoint Inc., family members said.Johnson's mother, Ann Johnson Smith, issued a plea for help in the search for her son in a video posted on YouTube this week."It is very abnormal for Morgan to be gone this long," said Johnson Smith, who stressed that she talked to her eldest son at least every other day.The week before Johnson was last seen, his grandfather passed away. His mother said Johnson had arranged to take time off work to attend the May 24 funeral in Washington, D.C."Morgan was very distraught about his grandfather dying. He just was really emotional," she said.Johnson has a medical condition that requires him to take medication to prevent seizures. His mother said she does not believe he has enough medicine to sustain him this long."I am a concerned mom. I miss Morgan," she said. "I believe Morgan is alive, just disillusioned due to his medical condition."Family and friends have searched the areas around Johnson's hotel, and police asked that people check ditches and ravines, in case he suffered a medical emergency while driving.A Silver Alert was also issued in his disappearance.Johnson is black, 5 feet 8 inches tall, 155 pounds with black hair and brown eyes. He was last seen wearing blue jeans, a sweater and a black leather jacket.He is believed to be driving a 1995 four-door white Pontiac Grand Am with Indiana license plate No. JS1830.Johnson's friends and family have set up a Facebook page to raise awareness about his disappearance.Anyone with information about Johnson's whereabouts is asked to call Aldridge at 317-839-8700 or Plainfield police at 317-838-3565.