Why would he hide is presence from Yoda, a fellow Jedi? Sure you could say he would have gone into hiding but not before trying to regroup with the other Jedi. And surely he wouldn't just ignore the Empire and the Rebellion. It just doesn't make any sense, nor does it make sense to bring him back.
They didn't find him through the force because there are ways to hide your presence, one of which was utilized by Yoda on Dagobah.
But I would consider Windu a minor char too. Certainly not minor like Maul was, but still not that major.
And no he wasn't a major character as in Anakin, but he still said and did more than Maul and Boba put together.