Alt M : Merge.

some ways to maybe check
if you grab a line and it rips 2 points at same place apart then its not merged.
if you subdivide and it don't round then it's not merged.

shrink wrap also.

---

if blender has select connected

============================================================ 

The Artist that will fight for decades to conquer their media.
Even if you never know their name ,your know their Art.
Dark Sphere Mage Vengeance