Is it customary to mention it then? If the log of the engine that is currently installed is present, all is well!?
I should have deferred to Mr. Harbour to answer for his plane. I noticed on both of my planes the engine log is for the installed engine, and I have no log for the previous engines.
When an engine is removed for replacement the log for that engine stays with that engine and the replacement engine has it's own logbook.
An easy way to check if the original engine is still installed is to see if the first thing in the engine log says anything about an overhaul, removed from or installed on the air frame. Removal and installation may or may not be in the engine book however, the air frame log should show the installation of an engine with serial number xxxxx.