I dealt with theft a few years ago - put me off the hobby briefly - but most of the boxes held watches at the time, so insurance paid out. Somewhat ironically, the SMP I was wearing but lost the box and docs to, was then stolen in a mugging a year or so later.
These days I always keep them separate, hoping if anything ever happens again the branded boxes will be hastily grabbed and nobody notice the plain 'file box' I converted into a watch chest.
Can you complete the set to same degree as when it first left the store, regardless of who the first owner was? No, million to one odds. Higher maybe. Do you have the chance to grab an extremely desirable timepiece? Yes.
Only you know your personal tastes well enough to make the final decision, obviously. I will say I once bought a Timex for 15 bucks used, cash, and it still gets worn for gardening and lawnwork...because incidentally, I like it. No idea why, but I do. Another piece (I refrain from mentioning what, since I may soon sell) I got pre-owned but with full kit, on original bracelet, with two good quality leather straps and two NATOs for a total of four quality, barely if-ever worn aftermarket straps in addition. Nothing like a Daytona, just a solid well known and well liked workhorse of a watch. Despite the quality, the brand, the accessories, it just isn't doing a thing for me after almost a month of daily wear. So I'll probably sell it.
My point is that if you like the watch enough, the box and papers won't matter to you as much. But, if you're a collector who will sit there admiring a thing of beauty like this and think, "...if only I had the rest of it..." then I'd wait and find that, regardless of cost. Only you, if anybody, knows you that well.
Good luck and let us know what you decide!
