How do I know the SNPS which are removed when clumping are in a LD block or SNPs not existed in 1000 Genome

Hi everyone,
I’m not sure how to know why my SNPs are being removed applying clumping when reading the exposure data (in MR analysis). I would like to know as if the SNPs are being deleted because they’re not in 1000 Genome I can use proxies. And this way more IVs will be left for MR analysis. Does anybody take any approaches or we need to do it manually?
Any help would be appreciated
Paria