What happened to Chekov's confiscated phaser and communicator in Star Trek: The Voyage Home?

They fell into the ocean, at least according to the novelisation.

He grabbed the rail. He started to vault, then tried to stop short when he saw what lay below. His boot caught on the decking. He stumbled, bounced into the rail, tumbled over it, flung out his hands to catch himself. The phaser and communicator arced out and splashed into the sea. The wind caught his I.D. and fluttered and spun it away. His fingertips slipped on the wire cable. He cried out.

You might also want to note that the communicator was rigged to explode if it was opened by an unauthorised person.

Pavel tried to pretend he did not care about his communicator, while at the same time he tried to stay within reach of it and hoped desperately that they would not take it away to disassemble it. If he could get ten seconds with the communicator in his hands, he might still escape. But if his captors opened it improperly, it would self-destruct.

The film shows him leaving the communicator on the table but based on the info above, we can assume that it was eventually opened and then destructed itself. The ID badge has anachronistic information on it, but we can imagine that the materials were fairly mundane and are of little interest to the military.

I recall reading part of a novel where these items were recovered by the resourceful Gary Seven, presumably to be destroyed as anachronistic.

The stranger’s hand still rested on the handle of a partially opened drawer, while her other hand gripped the black, rectangular “radio” captured from Chekov. The remaining artifact, the one that resembled a handgun, still rested on the polished steel counter, just beyond the intruder’s reach.

...

The blonde woman smiled sadly. 'I understand what you're saying......But letting you people hold on to these gadgets is a worse idea than New Coke.'

_{^{"The Eugenics Wars-The Rise and Fall of Khan Noonien Singh - Chapter 31."}}

I know the books aren't canon but that seems as good an answer as any.