It doesn't need to work like your caucus did ,though.
A caucus is party driven, even if you go in and vote just like a primary. New Mexico held this sort of caucus.
A primary is state driven.
Why is a mail-in vote funded by the Dem party not an option?
That is an option. It would be a mail-in caucus.
And do the people who jumped shipped and voted in the Republican primary also get to participate in the Democratic caucus? That wouldn't be right.