I am a bit late to the party and kind of reluctant to be seen to pile in, but my input would be
1) Keep WorldTracer up to date but otherwise get on with your life. It really helps if you get a Tracer report at the airport but what you have done is the next best thing. No one looks for bags, except at very small airports.
2) Buy whatever you need to do your activities, in several years in this forum I'm only aware of one person not getting a fairly swift refund of purchases on BA (other airlines are very different!) and that was a case of someone taking the mickey frankly.
3) Bear in mind however that the £1200 or so limit is for the total claim, so you need to take that into account if you are claiming both for immediate needs purchase as well as fully lost baggage.
4) Fully lost baggage is now extremely rare, and generally happens when switching between airlines on complex itineraries, labels falling off, no address in the bag etc. Assuming you did properly label your bag on the inside and it's just a LHR-SJC I would be frankly amazed if it got lost totally. Due to the snow there is backlog at LHR but I guess by the middle of next week it will be sorted out.
5) Photo receipts and store them somewhere: finding a receipt after travel can be tiresome.
6) Twitter can be useful for specific, problematic situations (e.g. checked in at the gate and then not making transfer connections properly, perhaps the label fell off).

In terms of the next time:
1) If it's an item which is critical to your trip AND irreplaceable in a short time span, always take it hand luggage
2) Always expect a 1 or 2 day delay on baggage so take some provisions with you for that
3) Always put an A4 sheet on top of checked bags (inside it) with contact details, particularly SMS and email.
4) Personally I would not lock your bag, or instead to use zip ties, but I know some people just can't bring themselves to do this.
5) Insure, or self insure, if travelling with significantly more than £1200 worth of items
6) Photo your items before travel so you know what you're expecting, or photo once in a while, if mostly you'll be taking the same stuff. Just place all the items on a bed, photo, then pack (it will usually pack better that way too).
7) One of the airlines irritating little habits is asking for the original receipts of things lost. Point 6 will partly help with that, but for the 6 or so most valuable items there may be a case for retaining/photo the relevant receipts.
8) Be aware of the difference between replacement value and "as new" value, and if necessary insure / self insure for that. Realistically a 4 year old pair of jeans may have cost £40 when purchased, but the airline is unlikely to give you a tenner for that now.
9) Be aware of the usefulness of retaining information in the Cloud / Google Documents / Drive etc - you can then access receipts, photos etc from any computer anywhere.