Hi all - apologies if this has been posted before (did a search and couldn't find anything) however my 3 month old iPhone 7 today inexplicably ran out of battery power frighteningly quickly.....I am fanatical about closing apps so couldn't work out what had happened - when I double-clicked on the home button as usual - a greyed out STRAVA icon was at the foot at the screen stating "based on your current location". (see image below)

Have never see this before (I use STRAVA daily).....swiping up simply re-opened the app. restarted the iphone however was still there.
I then rode home tonight from the office (logged by STRAVA)....finished the ride to find it had vanished - and now the Faceboook icon is there!

am I missing something obvious?! is it something within my settings? i haven't changed or updated anything since yesterday - need to sort this as can't tank the batter life like this daily!

TIA for any advice....