Lille has recently switched to only allowing smart cards for tickets, the old paper tickets have been phased out. (No-one's updated their English language pages on tickets for that however...). As detailed on the French ticketing page, there are three kinds of smartcards you can get - a personal one (with your name + photo), a non-personal one, and a simple rechargable ticket.
With the personal and non-personal cards, you can load different kinds of tickets onto the card. For example, you can buy a set (virtual carnet) of 10 single journeys, and a day pass, and have both on your card. When you touch in at the start of your journey, if you have multiple valid tickets available, you're then prompted to pick which one you want to use. Details and pictures are in French on the Valider avec Pass Pass page.
However, that's the theory.... In practice, today I loaded a one day ticket onto my pass pass card, went to the validator, touched in, and it asked me if I wanted to use one my 10 single tickets, or the day pass. There's no buttons on the validator, it's a touch screen. I dutifully pressed on the screen over the box containing the text "Pass' Journée". Unfortunately, it seems that the screen wasn't well calibrated, as the box 5cm higher up labelled "10 Trajet Unitaire" lit up, and it gave me the big green tick saying I'd used a single journey.
So, in the short term, is there any way to get my journey re-coded to use the day pass, and get the single journey loaded back on? And in the long term, how do I make sure the correct ticket gets picked even if I come across another badly calibrated validator screen?