the tmpdir which usually falls in C:\Documents and Settings\<user>\Local Settings\Temp\vmware-<user> where you will find other generic VMware logs getting saved (ex : virtual center related). For VDDK (as per the documentation) this parameter has to be explicitly specified under the configfile as below :

. tmpDirectory = "<TempDirectoryForLogging>"
. vixDiskLib.transport.LogLevel = "<logLevel>" (the default <logLevel> is 6)
. vixDiskLib.nfc.RequestTimeoutMs = "<NfcRequestTimeoutInMilliseconds>"
. vixDiskLib.nfc.ReadTimeoutMs = "<NfcReadTimeoutInMilliseconds>"
. vixDiskLib.nfc.WriteTimeoutMs = "<NfcWriteTimeoutInMilliseconds>"

A definition (location) of the config file is not mentioned in the guide, so my assumption is you would need to manually create one and point to the same on your code. but i am again not very sure.

Sorry, if i'd missed that. But as i said before, there isn't a pre-defined thing within VDDK code that asks the logging to be happening in the tmpdir. Thats defined when you provide the init() statement, right? (by specifying the config file parameter)
So, if you have provided your own log functions, then by default, the only logs you may expect to find in the temp dir are the regular VMware logs / VC logs etc. Again thats what i am assuming looking at the guide, i agree there isn't a complete explanation on this given. But when i look into the location of the temp folder i do see logs with name vmware-<user>.log, which are mostly VC related logs. Is that the case?