You have (3) potential scenarios with this calf:
1) Since the scur gene is recessive in females and dominant in males, assuming the sire and dam are homozygous polled (as they should be if they are 1A Red Angus, possible to be hetero in 1B), the scur gene came from the dam as she can be a silent carrier while the sire cannot.
2) The sire was scurred and they were removed, and someone was less than honest.
3) The calf has a different sire than you think he does.
That said, I would do a parentage test on this bull (very cheap though RAAA) if you are planning on using this bull for a sire. If you are planning on using him for 1A seedstock production, please reconsider. I know genomically he is what you are after, but you have to look at the rest of him too. Maybe his picture doesn't do him justice and maybe I have a heavier bias against scurs vs. ineligible white, and before Doc jumps on his single trait selection soapbox, if he were mine he would be cut for those scurs.
What are your calf's bloodlines?
Edit: there are thoughts that that are more than one set of genes that result in scurs which could complicate things further, but to my knowledge those genes and their inheritance have not been yet sorted out. Perhaps Randi will chime in on this thread.