"doit" + past infintive vs "a dû" + infinitive to translate "must have ..."

Question

To translate "She must have found a great hiding place." I used:
"Elle doit avoir trouvé ..." but only "Elle a dû trouver ..." is listed as answer.
After some searching, I found a post on this forum that indicates to me that the two variants should both be valid in this context:https://french.kwiziq.com/questions/view/ca-a-du-etre-vs-ca-doit-avoir-ete.
On the other hand, in "A comprehensive French Grammar" by Glanville Price it says:
"Note that, where English uses ‘must’ and the past infinitive, French usually has a compound tense of devoir and the present infinitive (cf. 508,iv), e.g.:
Il a dû partir
He must have left"
Opinions?
Should one prefer the construction with "a dû" for suppositions about past events?

Accepted Answer

Bonjour Christian,
In this particular case, both options ("Elle doit avoir trouvé ..." - "Elle a dû trouver ...") are possible. Thanks to you, the former has now been added as a correct option. Be aware, both options are not always equivalent or possible.
I hope this is helpful.
Bonne journée !

Answer

Bonjour Christian,Interesting point!The observer makes a supposition/speculation/theory which is a completed past action in the mind of the observer at the time that it is made.This is why I see the case for "a dû trouver" as being acceptable over the past infinitive "avoir trouvé"Also, devoir is a transitive verb so needs an object to complete its meaning -- perhaps "trouver" acts as a direct object in this case?It is true however that the direct translation from the English would lead one to use "doit avoir trouvé".Unfortunately, your link didn't help because it relates only to this query.I look forward to a comment from an expert staff member.Bonne JournéeJim

Answer

Bonjour Jim,thank you for your reply and sorry for not providing the link correctly. Here is the correct link:https://french.kwiziq.com/questions/view/ca-a-du-etre-vs-ca-doit-avoir-eteSorry also for causing confusion by eliding the sentences. The full sentences would be:Elle doit avoir trouvé une excellente cachette. Elle a dû trouver une excellente cachette.Christian

Answer

Bonjour de nouveau Christian,
Thanks for the clarification.
Trouver is also transitive so it is now clear that the direct object is une cachette.
I also note that both constructions are possible so we have both gained some knowledge from the discussion.
Bonne journée
Jim