Yes mono can still be contagious even after the symptoms of mono go away.
It's estimated that you can be contagious for 2 to 5 and even 6 months with mono even after the symptoms have gone away and have stayed away.
So you can still likely catch mono from someone for up to 6 months once the persons symptoms of mono have gone away.
In some studies it has been shown that some people have even been contagious with the mono for as long as 18 months after the mono symptoms have gone away but that's rare.
Still you can likely catch mono from someone 18 months later.