I believe it is a standard treatment for neuropathy in conjunction with vitamin B12, did you take both or just the ALA?
Also I am a little surprised by your "two flavours" comment.
The terms r(+) and s(-) or R and L are used to describe compounds which exist as two different shapes, each of which is the mirror image of the other. These are properly called enatiomers and such compounds are said to be "optically active"
No need to go into this in any more detail - think of it having a left-handed and a right-handed form.
Under normal manufacturing conditions there is no reason for one form to be formed over the other, so conventional synthesis will result in a 50;50 mixture of the two forms, properly described as the racemate, or racemic form.
It is possible to make a pure, single enantiomer, but only by either destroying the other, or by using a starting material which is itself a single enantiomer, so pure enantiomers are considerably more expensive to make than the racemate.
So what i am getting at is this. It may well be that the r(+) form is the one we want, and a manufacturing route will probably exist, but yes, it will be dear.
The alternative may well a racemate in which case taking it would mean half of it would be useful to you, the other half would not, but it is unlikely the impotent half would do you any harm.
I don't actually know what I am taking, TBH, but I now aim to find out...