There are several different progress levels that you go through, Each of which are displayed at the end of a match unless specific conditions are met.
The main one for you right now is your level, which is mainly a measure for how much Gwent you played in total. You gain some small things after every level and are allowed to access ranked play once you reach level 10. You gain experience for that after every match and also after every match the bar should be displayed for this, no matter what. For the first ones, there may be additional restrictions based on the tutorials for the game.
Additional progress bars that are displayed after matches is the daily progress and once you get to ranked play, your progress trying to reach the next rank. Daily progress gives you extra rewards based on rounds you have won every day (the big points you may want to reach are 6 and 18 rounds in total). That one can reach a maximum of rewards once you won 42 rounds in a day (does not sound like you reached that).
So to answer your question:
You get levels by just playing, even if you end up loosing. You should always see your level progress bar after a game. Not sure why it would not show up. It is possible you mistook the daily progress bar for the level progress bar, the daily progress "resets" after you won 6 rounds because you finished the first tier of daily rewards (and got 100 ore).
