You can use contains to search in attributes indeed. But this is case sensitive. So if you really want to search case insensitive, you need to save your attribute in the same format as you're searching. For instance, you could store your attribute into a lowercase attribute with toLowerCase($Attribute) and then you can search exactly with:
[contains($Attribute,$Search/Text)]
If you don't do this, you will miss some results because of differences in cases.