Law enforcement sources tell TMZ they were called to the "Teen Mom" star's home Thursday night around 8 PM about the missing teen. Jenelle told officers Jace snuck out of the home through a window, and didn't have a cell phone with him.

What's most frightening, Jenelle's home is surrounded by woods, and Jace left in the night.

It's been close to 16 hours since Jace first went missing, and he's still out there ... cops tell us he's been added to a nationwide database for missing persons.

Thursday's escape isn't the first time Jace has gone missing. TMZ broke the story in early August when Jace went missing after school, he was found a few hours late. We were also first to tell you when he went missing from Jenelle's home again in late August but was located shortly after that as well.

Jenelle has chalked the runaways as Jace being a normal teenager, mad at his parents ... but there's clearly something more going on.

Do you think Jenelle Evans should still have custody of her child Jace after his 3rd attempt to run away? Vote below.