Large (ish) Black Downward Arrow over System Tray??

Hi everybody
I have a Surface 3, and my daughter (18 months) recently got ahold of it, and now there is a large (to me) black arrow over the sys tray...screenshot below. Its not linked to an application, as I've hidden some and it stays in the same place on the screen. Any ideas as to what it is and how I get rid of it? Searching here and google hasn't helped.

Thanks in advance.

~Jeff

A cold start may clear it. Use 'Restart' to make sure Windows does the full startup process. 'Shut down' and turning back on may not be sufficient as you are likely set to use 'Fast start-up'.

PS: my grandson once managed to disable the keyboard on my laptop (kids eh?).