Let's first figure out how you saved the tournament. The TD software will always prompt you to save your tournament before you exit the program, load another tournament, or create a new tournament. If you simply gave the filename a .csv suffix, that's not a problem - it still saved it in the software's internal format.
To truly get it in .csv format, you would have had to "Export" the tournament or players. Even if you did, the program would still have prompted you to save the tournament when you exited because "exporting" the tournament is not the same as "saving" the tournament, as far as the software is concerned. So, unless you were prompted when you exited the program and said "no" to saving the tournament, you're probably OK. Did you say "no" to the "The tournament has been modified. Would you like to save the changes?" prompt?