[Baalz]

Here's exactly the behavior I saw.
Take a turn for Dolphin, submit it correctly.
Receive receipt for Dolphin.
Take turn for Allegiance, accidentally include Dolphin's turn in reply rather than Allegiance.
Receive no receipt or problem notice.
Dolphin hosts correctly, Allegiance stales (I didn't notice that I never received a receipt until after the stale).

So, presumably at some point my Allegiance turn submission was rejected (it was the wrong nation, wrong era, wrong turn, etc.), but I didn't get a notice. Seems like you indicated I should get a notice if the turn was rejected, but I didn't so seems like a bug. Also, my suggestion above (which may not be necessary if you catch this type of error elsewhere) was to check that the attachment name "early_sauromatia.trn" matched the subject line "Dolphin, Sauromatia turn 21".