I'm gonna look past the lock-in tactic you tried and actually talk about 'locking yourself in.'
You already know the purpose of 'locking in' is to make sure you're in a position that prevents losing your girls in any way. Some methods use props, others use tactics.
I've realised a good way to lock yourself in is to actually LEAD.
Women love leaders, that's for certain. Leading these girls are small little commitments by them that can eventually turn into bigger commitments down the road (like...say...sex?).
Example in your situation:
(good song comes on) "Holy sh1t, this is an awesome song." hold out your hand and nod toward the dance floor "come on, let's dance"
if successful, you're leading them, therefore it's certain you're not going anywhere.