So I assume I found it via a search on Google or Pinterest such as "baby pants free sewing pattern".
The trouble now is that I can't identify where I got it from. I've used it a couple of times (having enlarged it on squared paper, and lengthened the legs). But I would really like to be able to acknowledge the source. I think it may not be English / American, as the centre front seam is marked 'MV' and the centre back seam is marked 'MA'. I'm not sure what those stand for, maybe something like milieu ventre and milieu arriere. (Though I am not saying this is a French pattern - I just have no idea.) At the bottom it says - 'Back to overview of patterns'. But if there was a hyperlink it has disappeared.
I've done all the searches again that I can possible think I might have used, but to no avail. I just can't find the pattern again.
If anyone recognises it, I would love to know where it comes from so I can say thank you!
On another post I will put the pants I've made using the above pattern (adapted a bit).
UPDATE: I've found it! It's a great pattern, and there are more on the same web Site. Thank you, Suzy!