If this has come up before, the Search function did not catch it, so...

Fortified Position is revealed. I play Lost Spearman from hand. Am I correct to assume that my opponent can't kneel one Influence to kick Lost Spearman back to my hand, because that would happen in step 4 of the action window, and as LS fully entered play in step 3, he is affected by Fortified Position's constant effect right away and therefore has his text blanked by the time he'd be returned to hand?

Now that I'm typing this up, I'm actually pretty sure this is how it works. But, you know, getting confirmation can't hurt, right?

You're right. Since Lost Spearman entered play, his text is blanked and your opponent doesn't have the opportunity to return him to your hand anymore.