This question has options. How would someone go about accomplishing this goal?
To prevent a bra strap from being visible on accident,

Pick from: * super glue the bra strap to the inside of whichever shirt you want to wear that day to prevent the bra from moving. * create a small strap of fabric with a button and sew it into your shirt to wrap around and conceal the bra strap.
create a small strap of fabric with a button and sew it into your shirt to wrap around and conceal the bra strap.