Unless it was another folkie who stole your CDs - and on the whole that's probably not too likely, I'd would think that they'd get rid of them quite quickly. Check the area around where you left the car - they might have been dumped nearby as soon as the thief had a chance to find out what they'd stolen. The suggestion about local second-hand/charity shops is also worth checking out.

I've had my car broken into several times and twice found the items dumped in the nearest hedge, because the thief didn't want them. I'm pretty sure that most of our local car-crime yobs would be terrified of the shame and loss of street-cred that would ensue if any of their friends found them in posession of FOLK MUSIC CDs !