Some cachers just log that when they log a cache. Either they are short on time, don't want to take the time to write anything but TFT$/TFTC but they have logged a cache and by doing so have thanked the cache owner, albeit a short reply.
Some cache owners are okay with that.. others are not. They would rather have an epistle of the days activities or difficulties obtaining the cache find. That's okay if you log either way... because Honey Badgers Don't Care!!
You can log this one anyway you like. You must sign the log though!!