more likely to have discharged due to damp/water on the contacts.................best to remove and clean if you have just washed the bike...............best to remove if you leave the bike in a damp garage. A lithium battery will only lose very small amounts of charge even over a pretty protracted timescale.
1st one went flat after 1 ride so I kept charging it.... the new "spare" lasts for 4 rides even if left standing. I think the first one was a dud but didn't realise and thought they were all like that.