Your experience of immediately losing your partner was due to it being a "mixer" dance - callers usually mention that when announcing a dance. It's very useful if (say) you're taking your small child up to dance, because while mine can mostly cope with dancing in a friendly set, there's no way they could yet go off independently.

No need to go hunting round the room for your partner at the end of a mixer to thank them - it's really not expected. (But in a set dance it's nice to.)

I agree with the other comments about having men/women in a set making it easier to spot where you ought to be at a given point. :-)