I understand they are not recognized during Agnatavasam as they lived in a different country as ordinary people and on top of it, they have the boon from yama. Even then, when kauravas see Arjuna (even in brihannala form) they suspect it is Arjuna.
But some how in Draupadi swayamvaram except Krishna no one could recognize them. Even Salya who is their maternal uncle could not recognize them and he fights Bheema.
Do they have special make up skills that no one knows 🙂
Who said, no one recognised Pandavas in Syamavara?
Yes, They didn’t recognise them before they came into filed for battle. Only, Krishna was known because he had great spies system like Yudhisthara & Vidura & Drupada had. And all other kingdoms had.
Dhritrashta also could have known if Vidura couldn’t be there. Vidura had hide that massage as he was handling the all spies system and country and Bhishma was also well known (as per southern text). Drupada also suspected them and so Dhristdyumna too (Vaivahika Parva). Karna also suspecting them while fighting. Brahmans and all others suspected them too.
Dhritdyumana said “Our hopes have clearly been fulfilled. We have heard that Pritha’s sons escaped from the fire. From the way in which the bow was strung and the target brought down with strength, from the way in which they conversed with each other, it is certain that they are Pritha’s sons, living in disguise.”
Shaly or Duryodhana or other could not suspected them because they were bully and foolish and can’t think that Pandavas can return from land of the Dead.
But, while suspecting them in Sabha, they cannot proved that they were Pandavas as definitely they hidden in Brahmana attire. Only, strength can’t define your identity.
In Agyatavasa first Drona suspected Arjuna and this shows how much he loved Arjuna and Arjuna loved Drona (Drona Vadha Parava).