There are various reasons why baptisms may be found in places other than the OPRs and therefore not searchable on scotlandspeople.gov.uk.
Sometimes baptisms were recorded in amongst the Kirk Session material. Also baptisms were sometimes performed by a non-Church of Scotland minister, such as a Free Church minister, and recorded in their register.
There is more information about the specific registers on our website.
As with all our indexes they are free to search, you only pay if you want a full transcription. Parish births/baptisms are just £1.50!