Galatic travellers will seldom mention their planet of origin. That circlip once identified will allow you to examine wherever it came from. Then you can examine to see if it is missing or has been replaced at it's source. Wise to run it down but generally I would not expect replaceing the engine at this point if it is running well is going to be an issue. Are the rocker shaft arms retained with clips of about this size?

I cannot identify that clips source but others will. It is almost impossible to be a retaining clip from the turbo. It would have had to be physically dropped down the chain area portal to make it to the oil pan if it was. I cannot see that happening.