Glad you got it sorted, and thank you for the follow-up.
Each song occupies its own folder under the MUSIC folder. The song folder contains all the track recordings for that song, plus the song settings such as input assignments, eq/fx levels etc., and also the master file for that song if you 'mixed-down'. It is completely independent from any other song folder.
When you 'load' a song, you effectively 'open' its folder, and any changes will be confined to that one folder. Mixing down creates (or overwrites) the master file for that song; the original track files remain unchanged.
You can load different songs as & when you like, so you can continue working on different songs without impacting others.
Not sure if this answers your question as you said you recorded 2 'songs' back-to-back. If you mean 2 Tascam songs, you would have created a new song for each of these recordings, in which case they will be completely independent as explained.... but if you mean you recorded a 2nd musical song within the same Tascam song, you will have added new track recordings to the existing song.
The first set of tracks are still present on the card, so it depends where in the timeline you recorded the second set. If they don't overlap, you should be able to move the transport to play them. If they do overlap, you won't be able to do this, but you can use the Undo system to recover them. This can get tricky as there is only a limited amount of history you can access from within the machine (although you can access old files using a computer).
There is only one master file for each song, so if you did 2 mix-down/master processes within the same Tascam song, it will overwrite the master file each time. Again there is an undo option, but this can only undo one level.
Bottom line is you should really create separate Tascam songs for each of your musical songs to avoid problems.