Unless of course they've got a spare Macbook that actually did belong to the woman, which she left thinking she was taking her own Macbook, but there's nothing indicating that this is the case.
So you've got two very clear issues. One is a passenger who stole $3k on broad daylight, who is on footage and can easily be traced to a particular flight, which can easily be traced to a passenger list, which can easily trace back to her.
The other is that you've got a custodial relationship for a few minutes. You give objects away to be inspected, at which point the TSA becomes a temporary custodian. They ought to return it.
I can imagine that the TSA restricts their liability to e.g. $5k per item, and that its liabilities are covered if and when it has a proper safe-keeping procedure in place that's followed, such they're not held accountable for 'acts of god' (which is a legal concept). This would provide sufficient incentives to create very simple procedures that'd prevent 99% of such issues, like described earlier in this thread in India. You have a box with two tags, you get one, the employee at the end gets one, you put stuff in box, you give tag, you take stuff from box, that's it.
But the notion that they're taking your stuff without any liability, responsibility, insurance, procedures or just in general, recourse, is ridiculous.