Thanks for posting this, this is very interesting! It's a shame you're not able to do some analysis of how certain TB features (material, size, etc.) correlate with survival rate - I would be curious to know if this dataset could verify some of the longevity strategies, or potentially even suggest new ones - but I appreciate how much extra work that would be on top of how much effort it must already take to keep this updated, so it's understandable!
One thing that might be comparatively easier to graph with your spreadsheets as they are, but still very interesting to know, is this: for a given interval between logs, how often does that interval end with the trackable being marked as missing (vs. being successfully dropped, grabbed, etc.)? So if someone is watching their trackable that hasn't been logged in, say, 3 months, they could get an idea of the odds that it'll turn up again. Presumably, the longer it is before a trackable is logged again, the more likely it is to have gone missing - although sometimes they do indeed re-emerge after a surprisingly long time!
Would you consider publishing your spreadsheets (or just the raw data) somewhere, eg. GitHub, or do you prefer to keep it private?