Patrick's car ended up in a ditch about 30 to 40 feet off I-94, but didn't crash, Indiana State Police Sgt. Rick Strong told CNN on Thursday.
Investigators used dogs to track the driver.
"(The dogs) indicated that whoever was in that vehicle ... tracked back to that roadway" roughly 30 feet from the car, Strong said.
The dogs sensed no trace after that.
"We have scoured, searched, and looked at everything we could possibly look at -- all the exits, all the businesses, all the hotels," Strong said. "We posted fliers, we talked to neighbors (who live near the highway). We did a full-blown on-the-ground search in the wooded area north of where the car was."
"We looked everywhere" but have so far come up empty, he said.
http://www.cnn.com/2013/12/19/us/michigan-indiana-doctor-missing/