Spotify iOS app says 'Playing on Echo' when I'm not at home

I'm experiencing a weird issue and hoping someone can advise on how to fix.

My Spotify is connected to Alexa as my default music app. This morning when I was getting ready, I asked Alexa to play something on Spotify. When it was time to leave for work, I asked Alexa to turn off, which it did.

Now whenever I open my iOS Spotify app, it will automatically start playing the track that was last playing on my Echo when I left earlier. It's playing on my phone, through my headphones, but it still has the green remote playing icon, with my Echo listed next to it.

I can't seem to be able to 'disconnect' the Echo from the app so I can control what I'm listening to on my phone. All the tracks are greyed out, and all I can do is play the track/album that was last playing on my Echo.

I've looked in the Alexa app to see if there's any way of controlling the Echo that way and stop it from playing Spotify but can't find anything. There's nothing in the iOS app to disconnect it either, tapping the green icon just shows the pop up that says "Listening on Echo" with no exit or turn off button or option.

Am I missing something obvious here or is it a bug?