I ran across this on Reddit and thought it would be worth sharing since there is a good chance this missing 18-year-old could still be in Sioux Falls. The poster did not give the name of the missing person. This was written by the boy's father. It is not quite clear from the post if the father is in Texas, or in Sioux Falls:

My son has been missing since Oct. 28-29th 2014 from Sioux Falls, SD. A missing person's police report has been filed as of Oct 31-Nov 1, 2014 when I had not heard from him for a few days, if anyone knows anything or sees him, please contact the police in Sioux Falls SD.

My son is from Texas he was duped into getting a bus ride up to SD to meet some girl off of fb, and was presently up there when he was last seen last week.... he is also presently not dressed properly for the cold SD weather as he was dressed for the weather in Texas of shorts and t-shirts when he left for SD. He had received some items from local shelters to dress warmer however he has never lived or been in such cold weather before.

He has a severe mental handicap, he is autistic and has a heart condition, he requires medication for his mental state and he is presently off his medication. He is 18 with the mentality of a 12 year old. He's 5 ft 7-8 in. around 140-150 lbs with dirty blonde-brownish color hair, brown eyes. His right shoulder has a odd position to it and sets lower than his left shoulder from where a few years ago he broke his clavicle in two places (after being struck by a car) and it never healed quite right.The first knuckle on his middle finger has a slight crook to it where he broke it when he was younger. He has small scars on the left side of his eye in the eyebrow and below his eye where he was bitten in the face by a dog they are not noticeable in photos but can be seen when in person. Here are the most recent photos I have of him including one from his current school ID before he hopped the bus to SD.

It is at that point that the story gets even more bizarre. The posting goes on to say that the missing boy may have fallen into the hands of someone else:

We fear he may have fallen prey to a 36 yr old man that he was acquainted with as this man was one of the last people to see him the day before he went missing after a police report was filed as this man had a confrontation with him.

Please keep an eye out and Share with anyone who may be in the area. We want to know if he is safe or not." - Reddit contributor bamfsEnnui

An update was posted on Tuesday, Nov. 4th:

I have received reports of rumors of him being seen Thurs or Saturday last week at one of the local shelters but no proof for sure of it, he still has not been found."