If a sidenav component is in an open/active state when a resize occurs and the resize causes the sidenav to go be hidden (for example hide-gt-sm is applied), I would expect the nav handle itself needing to enter a closed/nonactive state. Additionally, you can request to toggle the sidenav into an active state while it is hidden.

Both can be replicated here: http://codepen.io/josephperrott/pen/jbbpEq

Reproducables

Resize:
Open the page and size the window small enough for the sidenav to be available, toggle it open and then resize the page large enough for the sidenav to be hidden. The backdrop remains present, it then requires a click anywhere on the page for it to "close".

Toggle:
Open the page large enough that the sidenav cannot be displayed, then click the toggle sidenav button. The sidenav stays hidden, but the backdrop appears.