Ummm, no. A unit that performs an emergency disembarkation may take no further action for the turn that they emergecny disembark. That's PLAYER turn, not game turn.
So for the OP, your sternguard would have performed an emergency disembarkation as laid out on page 7, and then they could act normally on your turn. Additionally, there is absolutely nothing preventing you from disembarking into the ruin (assuming your using the term as defined in the rulebook, page 77, ie a ruined building you can move around in.
Edit: Darn fat finger typos. Disembark rules page 67...................