I believe that a single unreturned heartbeat will do that, yes.
What do you mean by “manually”?
If you mean using the HTTP(S) API then no, it does not.
If you mean that your device wakes then connects to Blynk then the server knws that the device is online again and what you call the “ping timer” is re-initialised.
It might help if you turned BLynk Debug on and watched the data exchange between the server and the device. This topic might help you to understand the results…
Pete.