I think the engineer was
not stalking her in any sense that matters. Looking up information on someone could be considered “stalking”, but if there was no likely bad outcome from it, then it’s harmless. In the same way, sneaking into a movie theater without a ticket is usually a bad thing, but if you actually bought a ticket and then you accidentally dropped your ticket in the gutter, your sneaking in is moral and acceptable. It’s all about the expected result, not the means you use.
Why is “stalking” a woman bad in the first place? Because the stalker might get so obsessed that they get violent with or rape the woman. Or because the woman might feel like her privacy has been violated. Or the woman might feel nervous around the stalker, not knowing what they want.
None of these bad situations were going to result from this type of information-gathering. The engineer was not planning to hurt this woman or interfere with her in any way. The woman would not feel that her privacy has been violated, because they just want her name, and the woman probably wouldn’t mind if the bet-taker just told the engineer her name. And the woman knows what this “stalker” wants – to win a one-time bet. So she won’t be nervous about his intentions – winning a bet to find out a name is a harmless action that does not inspire worry.
As for posting her information online, yes, it seems like the engineer had an unintentional privacy leak in that they showed Facebook users from her high school her picture. (I don’t think he was purposefully lying about posting her info, I think he just didn’t consider the photo significant.) Showing the photo could be bad if the woman didn’t want anyone seeing that dress she bought, or didn’t want her alumni to be reminded of her. You could argue that showing the photo to those users was a mistake on the engineer’s part.
But you should keep in mind that the chances were pretty low that this woman’s picture leaked anything significant to her former high school classmates. It’s very likely that they didn’t care what dress she is wearing. Many of them saw her face already when she was actually in high school, and as for the ones who had not, seeing a normal photo of a random woman in a dress is unlikely to cause anything bad. There was a possibility, but it was very low.