Problem: unit ramdomy lost after a my attack on castle due to time limit

[Regirs]

Heya I lost my full unit stack(parrot guns) after a battle even though during a battle none of my units were even scratched.
It was a little bit a ruse I conjured; had 2 parrot guns units decimating forces of enemy castle I attacked while holding my other forces in a safe distance, then instead of taking a castle(still a lot of enemy left) decided to wait while time is up with 60min battle limit, then attack in a next turn with all my troops untouched and only half of their forces remaining. How surprised I was with my "valiant defeat", that in an after battle information screen said that I lost one of my unit- parrot guns(sic!)

So my question is is that a normal thing? anybody knows?

[Regirs]

ok -update when I started battle in next turn it turned out parrots guns I lost are on the enemy side(sic!)

[Pathfinder]

You should have withdrawn all your units rather than let the timer run out, which lets the enemy win by default. Units left on the battlefield when defeated have a chance of being destroyed, or in the case of artillery, captured. If you start up a battle and immediately quit it for example you will lose units regardless that none even engaged. Units successfully withdrawn will be spared regardless of battle outcome.

[Man o' War]

As the attacker you must win the battle before the timer runs out or you will lose.

As the defender you only need to survive the battle until the timer runs out to win.