Let's walk through it.
"Declarer exposes her cards and claims without a statement". No statement at all? Okay, fair enough. This is definitely a claim (Law 68A). Failure to provide a line of play statement is an infraction of law 68C ("A claim should be accompanied at once by a clear statement as to the order in which cards will be played"). Play ceases (Law 68D). Presumably West now objects to the claim, since he has a trump. So the Director is called, and he will, as Law 68D requires, apply Law 70. Law 70A requires the director to be "as equitable as possible to both sides" while giving the benefit of any doubt to the non-claiming side. Law 70B tells the director how to proceed:
1. Require claimer to repeat his line of play statement. This is not an opportunity to come up with a statement. Claimer didn't make one, so the only correct action by claimer at this point is to 'fess up: "I didn't make one".
2. Hear the opponents' objections (though his considerations are not limited to those objections).
3. The Director may require the players to place their cards face up on the table.
Okay, now what?
As the OP suggested, Law 70C is germane. Here's that law:
Quote
Law 70C: When a trump remains in one of the opponents’ hands, the director shall award a trick or tricks to the opponents if:
1. claimer made no statement about that trump, and
2. it is at all likely that claimer at the time of his claim was unaware that a trump remained in an opponent’s hand, and
3. a trick could be lost to that trump by any normal* play.
* For the purposes of Laws 70 and 71, “normal” includes play that would be careless or inferior for the class of player involved.
Claimer made no statement about the trump, since she made no statement at all. OP asserts that "she's probably not aware of the outstanding trump" but gives no evidence in support of it. So what evidence do we have? Well, we have the evidence that she didn't say anything about it. Normally if a player knows a trump is outstanding, she'll say something about (particularly if she's run into this problem before). So I'd say the criterion here is met: she may well have been unaware. Could a trick be lost by any normal play? The footnote tells us that on a diamond lead ruffing with the ten would be "normal" as it is certainly inferior, and also careless. So this criterion is also met.
The rest of Law 70 is either irrelevant to this particular case, or reinforces the correct ruling per Law 70C: the criteria of Law 70C having been met, one of the remaining two tricks goes to the defense, and one to the declarer.
Earlier I mentioned that declarer violated Law 68C in not making a line of play statement. That law says a statement "should" be given, so the Introduction to the laws tells us that a procedural penalty, while possible, would be rare. I don't see a reason to give anything other that a warning in this case.