The phaenomenon exists in the Ionic dialect. If you study Herodian's works, you will find most dialectal variations in grammar. Particularly, to answer your question, I can recall at least this one example (there are more) that does not take the ἐ- augmentation: the Ionic form φάμεν, instead of ἔφαμεν.
If Eustathius Phil. is quite right, then the phaenomenon is more general and conceptual, i.e. the augmentation is absent from both Imperfect and Aorist; this would cover, for sure, the contracted verbs. See this excerpt of his:
῞Οτι οἱ ῎Ιωνες τὰς μὲν χρονικὰς αὐξήσεις τῶν παρῳχημένων κατασπῶσι συνάρχεσθαι τοῖς ἐνεστῶσι ποιοῦντες αὐτούς, ὡς προείρηται. οἷον ἀγαπῶ ἀγάπων, ὀρύσσω ὄρυσσον. ὡσαύτως καὶ τὰς διὰ τοῦ ε αὐξήσεις καθελόντες τὴν αὐτὴν ἀρχὴν περιποιοῦνται τοῖς ἐνεστῶσι καὶ τοῖς παρῳχημένοις, τοῦ τύπτω τὸν παρατατικὸν τύπτον λέγοντες καὶ τὸν ἀόριστον τύψα.
My translation (following a bit the original word-order):
= Because the Ionians the tense augmentations of the past do in a way, that they begin like the present , as said before. I.e. ἀγαπῶ ἀγάπων, ὀρύσσω ὄρυσσον. Likewise for the augmentations with ε, following the same principle they form both the present and past , saying the imperfect of τύπτω as τύπτον and the Aorist τύψα.
Well, this implies that if Ionians do so, they might have been using also contracted verb forms sometimes, which is quite contrary to the vast uncontracted forms. Yet the correctness of this has to be cross-checked.
Herodian says that this is an Ionian poetic form/preference in order to preserve the verse's metre. But his examples don't happen to include a contract verb, but rather verbs that begin with the 3 changing vowels, i.e. α, ε, ο. Those are ἄκουεν instead of ἤκουεν, ἔλαυνεν instead of ἤλαυνεν and ὀνόμαζεν instead of ὠνόμαζεν. It sounds - at least to me - that contract verbs beginning with those would do the same. Hope this helped a bit.