Losing Antifreeze out of DeGass

[herewegotogether]

Just had coolent system flushed and refilld. Pulled from Green Bay to St Paul Minn lost some fluid. I asked the dealer to check cap to make sure it was OK and holding pressure he just said the gasket looks fine and that if I am losing fluid it is a head gasket. that just doesn't sound wright. The truck is a 2005 F350 with 80000 miles. In May had compression test and no problems.

Thanks for the help
Bill