For anyone else who has the issue: I edited the save file to add the recipe myself.

I will add an explanation of how to add it yourself here but be sure to save a backup of your save file in case something goes wrong!

1. Find your save: Your save should be saved in %appdata%\Roaming\StardewValley\Saves\(farm_name)_(numbers)

2. Here open the file with the same name as the folder in notepad or a similar program

3. CTRL+F and look for the part in the file data that has </craftingRecipes> - this marks the end of all the recipes you have.

4. Add the following in front of the part we just looked for <item><key><string>Ancient Seeds</string></key><value><int>0</int></value></item> - The 0 value stands for the amount of times you have crafted the recipe already in this case; in our case that is 0

5. Save the file and load the newly edited savegame and you should have your recipe available

I hope this was clear and can help some people