Question about Samsung Galaxy Tab S2 Value Edition

I set up this tablet last week, but because I haven't used it for 24 hours, it's demanding I enter a password. Problem is, it's not working. And I can't hard-reset the device without powering it off first... which it won't let me do without entering the password. And there's no "Forgot password?" option. What the heck can I do (other than waiting for the battery to die completely) ?