I imagine this is very much the case. I don’t imagine the searches are “fishing expeditions” as it were (see what I did there?!). I suspect they want to complete the evidence trail as much as possible so want to account for as many of her belongings as possible. Now, this might end up being futile (they may never find it). But i guess their thinking is, we know we are missing x, y, z so whoever did this must have disposed of them. I reckon they are searching areas linked to the accused. If they have tracked his movements via his phone, car gps or local cctv and THEN they find her belongings, then he has even more of a case to answer.
Now, there is every chance this could backfire (ie a g public search is being carried on somewhere with the intention of finding something - if they don’t find it then it’s less evidence. But I suppose just because - and let’s for argument’s sake assume it is a phone- they don’t find it; doesn’t mean it wasn’t there. But it is just one less piece of evidence they would probably like to have.
IMO this might suggest they have less physical evidence than they would like. But TBH we don’t know what they have so it would be foolish to speculate otherwise as to the strength of the case and if this guy is completely innocent and he had nothing to do with it, then better to know for his sake that everywhere is searched properly or to find the phone which may have other evidence on it. Because if he is innocent then there would still be a murderer on the loose.