Easy enough to check for Current drain ; IF you have an Ammeter.
There are 2 types. Easiest to use is the Clamp -on type. Has jaws that open and close and you merely open them up,put them around your Active wire (positive or power wire),set the scale to milliamps and DC and see if there's any current flow ( some sort of reading). Some of the better ones don't even require the operator to set them for the Current OR voltage. That's taken care of by the instrument.
The second type and probably more common ,are those with Red and Black leads that are plugged into the unit and then across terminals or whatever it is you're testing.
This type-like all Ammeters save the Clamp-on units, MUST be connected in SERIES.
That is, you will have to disconnect the Positive /Red/ Power lead from your battery, join/hook up/connect the Red Ammeter lead to the just vacated battery terminal and then join/ hook up/ connect the end of your lead that you've just taken off the battery to the black lead of the Meter.
The end result of this long-winded tale is that ANY current draining from your idle battery WILL flow through the Meter and hopefully you'll get a reading. In milliamps of course.
Do you have a Fuel Injected bike? The engine UCU will drain a battery as will an alarm system. They're both always "on". Passive, but still on.
How about any accessories that have been wired direct to an Active or power wire.Radios, or CB's or GPS's or such .Even a clock will drain a battery given enough time.
I would doubt a Short Circuit is the cause. In electrical terms a Short Circuit has huge current flow (compared with the "normal"operating current) and really should blow the Fuse protecting the circuit. And probably cause smoke, noise and a pungent burning smell.
You really should remove, scratch brush your battery connections-both the terminals and the lugs on the cables that go away to the bike- and put Dielectric grease on the nice shiny bits and tighten them all back up.
Wouldn't hurt to do the same to the other ends of the battery cables as well.
You do not want any high resistance joints in the starting system.
Go buy a "ctek charger" and hook that battery up to it.-even if you have to take it out of the bike.
Not intending to lecture you-if you're aware of this then sorry.
If you're not, maybe it will help.