Guys,
I've described it here:
https://stackoverflow.com/questions/18984972/phalcon-mvc-model-serialization-object-properties-are-lost
Basically, non-DB object properties of a Model don't get serialized.
Thanks, Temuri
It is a current behaviour of Phalcon model serializer.
A new NFR:
https://github.com/phalcon/cphalcon/issues/1285
Note, that the current workaround is override the default serializer.