I have heard many times of the omitting of the "ed". But someone suggested that it should never omit the ed.
Yes, it can sound like the /d/ is omitted in this context. This is an example of the so-called "elision" of alveolar plosives in English, as described in Araucaria's answer to the ELU question Pronunciation Deleting /t/ Between Consonants. Even native speakers may not be able to distinguish a /d/ or /t/ sound from no sound in this kind of context. But a native speaker's ears will usually automatically fill in hard-to-hear sounds like this based on grammar and meaning.
Even if you can't hear it, it may actually be present in the speaker's tongue movements--see user6726's answer to this Linguistics SE question: https://linguistics.stackexchange.com/questions/28276/what-books-give-a-comprehensive-analysis-of-intermorphemic-consonant-clusters-in. I would not recommend that a learner try to omit /d/ entirely in this context.