"left unknown" is a correct and usable phrase in written English.
You can use it when the outcome of an event or the identity of someone or something is not known or revealed. For example, "The cause of the house fire was left unknown."
"Anything that is unknown is better to be left unknown," said John York, the owner of the San Francisco 49ers.
A few years back, the creator of "Johnny the Homicidal Maniac" -- a comic about exactly what it sounds like -- was allowed to create a Nicktoon for reasons perhaps more amusing when left unknown.
The signal amplitude and rise/falling time of the signal changes depend on where the electrode is placed, and the gesture, however the pattern of the change is left unknown.
The testing set consists of patterns just represented by the input component, while the output component is left unknown and its value results from the ANN algorithm for that specific input.
It doesn't take Dear Abby to figure out that some things are best left unknown, and that tapping into your significant other's deepest emotions can create more problems than it solves.
We would rather leave unknown many of the erotic impulses that lie somewhere within us.
It turns out, however, that it can be rather difficult to find out from patients or research participants which genetic results they would like to receive and which they would like to like to leave unknown.
The technique used to identify the Merkel cell polyoma virus eliminates known human molecular sequences from a sample of tissue, leaving unknown or nonhuman sequences that the scientists explore in seeking a possible infectious agent.
A 43-minute video of Senator Clinton's Google session has been available since February and has drawn only about 54,000 "views," which count as soon as the video is begun but leave unknown the more interesting number: completed views.
Many wealthy donors have put their money into issue advocacy groups that are not required to disclose their identities to the Federal Election Commission, leaving unknown the true scale of outside money flowing into the 2012 campaigns.
