If tt5five thumbed the dive and if the DM signaled that they should stay with him (these are assumptions which may be incorrect), there was no miscommunication, rather, the situation would border on negligence.
@
Crush:
tt5five never specifically stated that he "thumbed" the dive. According to my training (PADI), thumbing the dive communicates a desire to immediately abort the dive. As
BabyDuck pointed out, the thumb should be acknowledged by the diver's buddy/buddies with another thumb gesture and the buddy team should be headed toward the surface. FWIW, I don't think that a buddy team thumbing a dive necessitates that the entire group being led by a DM should have to abort the dive as well.
On a side note, when it comes to a DM asking me to do something underwater that's dangerous (ignore turn pressure, ignore rock bottom, go deeper than the dive plan, follow him into an overhead environment, violate NDLs), I will interpret his words/signals merely as "suggestions" and follow my instincts to stick with whatever plan my buddy team agreed upon in pre-dive planning.
If
tt5five did, in fact, use his thumb to indicate
to the DM his desire to surface immediately, then presumably he was only doing it out of courtesy to inform the DM of the actions of his buddy team. If I were in
tt5five's shoes and had reached my turn pressure, I would have gotten the attention of the DM, pointed at my buddy and me, given the thumb sign or turn-around sign (depending on whatever action was more appropriate), and then waved bye-bye (to signify that we weren't in any distress).
If I wanted the DM to surface with me or my buddy (because one or both of us were in distress), I would point to the DM, give the thumb signal, and then give the "together" signal (two index fingers together). I probably wouldn't wait for the DM to respond since my buddy and I would be occupied managing our crisis.