I've created a spreadsheet that's now into sheet 3. When opening it yesterda, I could only get sheets 1 and 2 to come up. Sheet 3 goes to sheet 144 and it's a graph.
Is there any way to retrieve sheet 3 and its data?

You may have not properly saved this spreadsheet so page 3 just disappeared. That happened to me a few times until I got hip and started saving the speadsheet every other jerk. I know of no way to retrieve sheet 3 and believe me I pulled my hair out trying to retrieve my own missing sheets. It's gone. You'll just have to recreate this missing sheet. Sorry.