That is our fault, not Tindie's. Please accept our apologies.
I am more than happy to send you out another switch at no cost, but we haven't got any in stock. We have some arriving next week.
In the mean time, you can solder the holes to close the connection. Check the traces on the PCB to see which two of the three holes are used for the switch ( I haven't got one in front of me at the moment).
There is no issue leaving it on all the time. Infact, I never turn my test PiScreens off and I have one that has been running for 6 weeks straight and still going.
Mark --OzzMaker.com --