I’ve only deleted a few posts but the search feature sucks balls I’ve found. Let me know what you are looking for – I backup everything to WordPress and Word Doc. I can find the date it was posted and point you to it on Tumblr.
You can also go to https://the-romantic-dominant.tumblr.com/archive and look that way.
Last, this is a good link that helps you find things by day or order it differently: